WO2023167288A1 - Reducing agent, and gas production method - Google Patents
Reducing agent, and gas production method Download PDFInfo
- Publication number
- WO2023167288A1 WO2023167288A1 PCT/JP2023/007871 JP2023007871W WO2023167288A1 WO 2023167288 A1 WO2023167288 A1 WO 2023167288A1 JP 2023007871 W JP2023007871 W JP 2023007871W WO 2023167288 A1 WO2023167288 A1 WO 2023167288A1
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- WIPO (PCT)
- Prior art keywords
- reducing agent
- oxygen carrier
- carbon dioxide
- gas
- reducing
- Prior art date
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- 238000004519 manufacturing process Methods 0.000 title claims abstract description 19
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- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 104
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 96
- 239000007789 gas Substances 0.000 claims abstract description 94
- 229910002092 carbon dioxide Inorganic materials 0.000 claims abstract description 75
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- 239000002918 waste heat Substances 0.000 description 1
- 239000001993 wax Substances 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
- B01J23/76—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36
- B01J23/83—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with metals, oxides or hydroxides provided for in groups B01J23/02 - B01J23/36 with rare earths or actinides
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/40—Carbon monoxide
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F17/00—Compounds of rare earth metals
- C01F17/20—Compounds containing only rare earth metals as the metal element
- C01F17/206—Compounds containing only rare earth metals as the metal element oxide or hydroxide being the only anion
- C01F17/224—Oxides or hydroxides of lanthanides
- C01F17/235—Cerium oxides or hydroxides
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F17/00—Compounds of rare earth metals
- C01F17/30—Compounds containing rare earth metals and at least one element other than a rare earth metal, oxygen or hydrogen, e.g. La4S3Br6
- C01F17/32—Compounds containing rare earth metals and at least one element other than a rare earth metal, oxygen or hydrogen, e.g. La4S3Br6 oxide or hydroxide being the only anion, e.g. NaCeO2 or MgxCayEuO
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G49/00—Compounds of iron
Definitions
- the present invention relates to a reducing agent and a method for producing a gas, and more particularly to a reducing agent that can be used in chemical looping, and a method for producing a gas using such a reducing agent.
- a chemical looping method is used to convert (synthesize) carbon monoxide from carbon dioxide.
- the chemical looping method referred to here divides the reverse water gas shift reaction into two reactions, a reduction reaction with hydrogen and a reaction of producing carbon monoxide from carbon dioxide, and divides these reactions into oxygen carrier (for example, It is a method of bridging with a metal oxide: MO x ) (see the formula below).
- MO x-1 represents a state in which part or all of the metal oxide has been reduced.
- the reaction in which hydrogen causes oxygen vacancies in the crystal structure of the oxygen carrier is an endothermic reaction. It turned out to be a good thing to do. However, until now, investigations in the high temperature range (temperature above 650° C.) of the reaction that causes oxygen deficiency have been insufficient. In view of the above circumstances, the present invention provides a reducing agent that can be used in reactions at high temperatures, and a method for producing gas using such a reducing agent.
- a reducing agent that reduces carbon dioxide upon contact to produce a carbon value.
- This reducing agent is composed of metal oxides containing cerium (Ce) and transition elements other than cerium (Ce), and contains an oxygen carrier with oxygen ion conductivity.
- the peak position of at least one diffraction peak corresponding to the (220) plane in the X-ray diffraction profile corresponds to the (220) plane of cerium oxide (CeO 2 ). The peak is shifted with respect to the peak position.
- the reducing agent of the present invention is used in producing a product gas containing carbon monoxide (carbon value) by reducing carbon dioxide by contacting a raw material gas containing carbon dioxide with the reducing agent (i.e. , used in the gas production method of the present invention). Also, the reducing agent oxidized by contact with carbon dioxide can be reduced (regenerated) by contact with a reducing gas containing hydrogen (reducing substance).
- a raw material gas and a reducing gas are alternately passed through a reaction tube (reaction vessel) filled with the reducing agent of the present invention, thereby converting carbon dioxide into carbon monoxide by the reducing agent, Regeneration of the reducing agent in an oxidized state by the reducing gas is performed.
- the reducing agent of the present invention contains an oxygen carrier with oxygen ion conductivity.
- the oxygen carrier is a compound that can cause reversible oxygen deficiency, and the oxygen element itself is deficient due to reduction. It refers to a compound that shows the action of depriving carbon dioxide of oxygen element and reducing it.
- the oxygen carrier in the present invention is composed of cerium (Ce) and a metal oxide containing a transition element other than cerium (Ce). In such an oxygen carrier, the synergistic effect of Ce and the transition element promotes the production of carbon monoxide from carbon dioxide.
- the peak position of at least one diffraction peak corresponding to the (220) plane in the X-ray diffraction profile is the (220) plane of cerium oxide (CeO 2 ). are shifted with respect to the peak positions of the diffraction peaks corresponding to . That is, when X-ray diffraction measurement is performed under the same conditions for the oxygen carrier and cerium oxide, the peak position of at least one diffraction peak corresponding to the (220) plane of the oxygen carrier in the X-ray diffraction profile is the same as that of the cerium oxide.
- the timing of the X-ray diffraction measurement is before the reducing agent is used for the reaction with the gas, that is, immediately after the reducing agent is produced.
- the crystal structure of the cerium oxide crystal is stabilized by solid solution of the transition elements other than Ce, and the heat resistance temperature is improved.
- the reducing agents of the present invention can be used even at high temperatures above 650°C.
- transition elements other than Ce are dissolved in cerium oxide crystals
- the crystal structure is considered to be more stable when used at a temperature higher than 650°C rather than when used at 650°C or lower.
- Ce is alloyed with transition metals and tends to form a stable crystal structure, so that initial activity can be easily maintained even after repeated oxidation-reduction of the reducing agent.
- the diffraction peak corresponding to the (220) plane of the oxygen carrier is shifted to either the high angle side or the low angle side with respect to the diffraction peak corresponding to the (220) plane of cerium oxide (CeO 2 ).
- the diffraction peak corresponding to the (220) plane of the oxygen carrier shifts to the high-angle side or the low-angle side, or the amount of shift depends, for example, on the conditions for producing the reducing agent (in particular, pulverization time and , firing temperature and firing time).
- the shift amount of the peak position of the diffraction peak corresponding to the (220) plane of the oxygen carrier with respect to the peak position of the diffraction peak corresponding to the (220) plane of cerium oxide (CeO 2 ) is 0.1° or more in 2 ⁇ and 0.1° or more. It is preferably less than 6°.
- the lower limit of the shift amount of the peak position is 0.15° or more, 0.2° or more, 0.25° or more, 0.3° or more, 0.35° or more, 0.4° or more in 2 ⁇ . good too.
- the upper limit of the shift amount of the peak position may be 0.55° or less in 2 ⁇ .
- the lower limit value and the upper limit value can be arbitrarily combined to define a preferable range of the shift amount of the peak position.
- the shift amount of the peak position By setting the shift amount of the peak position within the above range, it can be considered that transition elements other than Ce are more sufficiently and reliably dissolved in the cerium oxide crystal. If the shift amount of the peak position becomes too large, the fluorite structure, which is the crystal structure of cerium oxide, may not be maintained.
- a specific diffraction peak corresponding to the (220) plane of the oxygen carrier preferably exists in the range of 2 ⁇ from 44° to 52° in the X-ray diffraction profile, and in the range of 2 ⁇ from 46° to 50°. It is more preferable to exist, more preferable to exist in the range of 47° or more and 49° or less, and particularly preferable to exist in the range of 47.6° or more to 48° or less.
- This specific diffraction peak corresponds to the diffraction peak corresponding to the (220) plane of the cerium oxide crystal in which the transition element is dissolved.
- a diffraction peak corresponding to the (220) plane of the oxygen carrier (especially a specific diffraction peak) has a full width at half maximum of preferably 0.3 or more, more preferably 0.35 or more, and 0.4 It is more preferable that it is above.
- the full width at half maximum is preferably 0.7 or less, more preferably 0.65 or less. This means that the increase in crystallite size of the oxygen carrier is suppressed, in other words, the crystallite size of the oxygen carrier is kept relatively small.
- An oxygen carrier with a relatively small crystallite size shortens the migration distance of the oxygen element, so both the reduction reaction of the reducing agent by the reducing gas (inducing reaction of oxygen deficiency) and the reduction reaction of carbon dioxide by the reducing agent are promoted. be able to.
- the specific value of the crystallite size of the oxygen carrier is preferably 320 ⁇ or less, more preferably 300 ⁇ or less, even more preferably 280 ⁇ or less, particularly preferably 270 ⁇ or less, and 260 ⁇ or less. is most preferred.
- Such an oxygen carrier having a small crystallite size is preferable because the oxygen element travels a shorter distance.
- the lower limit of the crystallite size is not particularly limited, it is preferably 210 ⁇ or more, more preferably 220 ⁇ or more, further preferably 230 ⁇ or more, and particularly preferably 250 ⁇ or more.
- a reducing agent containing an oxygen carrier having a crystallite size below the above lower limit tends to be difficult to produce.
- the lower limit and upper limit can be arbitrarily combined to define a preferred range of crystallite size of the oxygen carrier.
- the full width at half maximum and the absolute value of the crystallite size, as well as the diffraction peak corresponding to the (220) plane of the oxygen carrier have a full width at half maximum It was found that there is a high correlation between the ratio of peak intensity to (peak intensity/full width at half maximum) and the reactivity of the reducing agent described above.
- the specific value of this peak intensity/full width at half maximum is preferably 6.2 or less, more preferably 6 or less, more preferably 5.5 or less or 5 or less, and 4.5 or less.
- the lower limit of peak intensity/full width at half maximum is preferably 2.5 or more, more preferably 3 or more.
- peak intensity/full width at half maximum is less than the above lower limit, the crystallinity of the oxygen carrier may become too low, making it difficult for the oxygen element to move.
- the specific diffraction peak is the peak having the maximum intensity observed in the range of 45° or more and 49° or less in 2 ⁇ in the X-ray diffraction profile.
- a ratio of peak intensity to full width at half maximum is defined for this peak.
- Oxygen carriers include transition elements other than Ce. Including an additional transition element in the oxygen carrier can moderately strain its crystal structure. As a result, the oxygen element moves in and out of the oxygen carrier more smoothly.
- the ratio (molar ratio) of the molar amount of cerium to the total molar amount of the metal elements contained in the oxygen carrier (metal oxide) is not particularly limited, but is preferably 0.6 or more, and preferably 0.65. It is more preferably 0.7 or more, and more preferably 0.7 or more. In addition, the upper limit of the molar ratio is usually 0.98 or less.
- the transition element is at least one element belonging to the 4th and 5th periods of the periodic table. Since the ionic radius of such an element is relatively close to that of Ce, it is possible to prevent or suppress the instability of oxygen carrier crystals due to the difference in ionic radius.
- transition elements include scandium (Sc), vanadium (V), chromium (Cr), iron (Fe), manganese (Mn), nickel (Ni), cobalt (Co), copper (Cu), zinc ( Zn), zirconium (Zr), niobium (Nb), molybdenum (Mo), ruthenium (Ru), rhodium (Rh), palladium (Pd), hafnium (Hf), tungsten (W), titanium (Ti), etc. be done.
- These transition elements can be used singly or in combination of two or more.
- the transition element is preferably one of Fe, Mn and Zr, more preferably Fe and/or Zr. Since these transition elements have ion radii smaller than that of cerium, they can moderately distort the crystal structure of the oxygen carrier and further improve the above effects.
- the oxygen carrier can also contain elements other than the transition elements.
- the reducing agent of the present invention may be composed of an oxygen carrier alone, or may be composed of an oxygen carrier and a binder that binds the oxygen carrier together.
- the latter embodiment includes an embodiment in which oxygen carrier fine particles are bound with a binder (carrier).
- the shape retention of the reducing agent can be further enhanced, and the specific surface area of the reducing agent can be easily adjusted.
- the ratio of the binder to 100 parts by mass of the reducing agent is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, and 40 parts by mass or less.
- the ratio of the binder is 1 part by mass or more, 2 parts by mass or more, 3 parts by mass or more, 4 parts by mass or more, 5 parts by mass or more, 6 parts by mass or more, or 7 parts by mass or more with respect to 100 parts by mass of the reducing agent. , 8 parts by mass or more, 9 parts by mass or more, or 10 parts by mass or more.
- the lower limit and the upper limit can be combined arbitrarily to define the range of the ratio of the binder.
- the binder is not particularly limited as long as it is a compound that is difficult to denature depending on contact with the raw material gas, reaction conditions, etc., but for example, inorganic materials such as oxides, nitrides, oxynitrides, and carbides, Examples include carbon materials (graphite, graphene, etc.).
- the binder is preferably an oxide, and an oxide containing at least one of magnesium (Mg), titanium (Ti), zirconium (Zr), aluminum (Al) and silicon (Si). more preferably aluminum oxide. These oxides are preferable because they are highly stable against heat and tend to stably bind oxygen carrier fine particles.
- the packing density of the reducing agent is preferably 4 g/mL or less, more preferably 0.5 g/mL or more and 3 g/mL or less, and even more preferably 1 g/mL or more and 2.5 g/mL or less. . If the packing density is too low, the gas passing speed becomes too fast, and the contact time between the reducing agent and the raw material gas and the reducing gas is shortened. As a result, the efficiency of conversion of carbon dioxide to carbon monoxide by the reducing agent and the efficiency of regeneration of the reducing agent in the oxidized state by the reducing gas tend to decrease. On the other hand, if the packing density is too high, the passage speed of the gas becomes too slow, making it difficult for the reaction to proceed or requiring a long time to produce the product gas.
- the pore volume of the reducing agent is preferably 0.1 cm 3 /g or more, more preferably 1 cm 3 /g or more and 30 cm 3 /g or less, and 5 cm 3 /g or more and 20 cm 3 /g or less. is more preferred. If the pore volume is too small, it becomes difficult for the raw material gas and the reducing gas to enter the inside of the reducing agent. As a result, the contact area between the reducing agent and the raw material gas and the reducing gas is reduced, and the efficiency of conversion of carbon dioxide to carbon monoxide by the reducing agent and the efficiency of regeneration of the reducing agent in the oxidized state by the reducing gas tend to decrease. On the other hand, even if the pore volume exceeds the upper limit, no further increase in the effect can be expected, and the mechanical strength tends to decrease depending on the type of reducing agent.
- the shape of the reducing agent is not particularly limited, it is preferably granular, for example. If it is granular, it is easy to adjust the filling density of the reducing agent to the above range.
- "granular" is a concept including powdery, particulate, lumpy, pellet-like, etc., and its shape may be any of spherical, plate-like, polygonal, crushed, columnar, needle-like, scale-like, etc. .
- the average particle size of the reducing agent is preferably 1 ⁇ m or more and 5 mm or less, more preferably 10 ⁇ m or more and 1 mm or less, and even more preferably 20 ⁇ m or more and 0.5 mm or less. With a reducing agent having such an average particle size, it is easy to adjust the packing density within the above range.
- the average particle size means the average value of the particle sizes of arbitrary 200 reducing agents in one field observed with an electron microscope.
- the "particle size” means the maximum length among the distances between two points on the contour line of the reducing agent.
- the maximum length of the distance between two points on the contour line of the end face is defined as the "particle diameter”.
- the average particle size is, for example, in the form of lumps, and means the average particle size of the secondary particles when the primary particles are agglomerated.
- the BET specific surface area of the reducing agent is preferably 1 m 2 /g or more and 500 m 2 /g or less, more preferably 3 m 2 /g or more and 450 m 2 /g or less, and 5 m 2 /g or more and 400 m 2 /g. More preferably: When the BET specific surface area is within the above range, it becomes easier to improve the conversion efficiency of carbon dioxide to carbon monoxide by the reducing agent.
- the reducing agent can be used in a wide range from low temperature (about 400 ° C.) to high temperature (about 850 ° C.). Oxygen capacity can be maintained at a high level. That is, the reducing agent of the present invention can efficiently convert carbon dioxide to carbon monoxide over a wide temperature range, and can be efficiently reduced by a hydrogen-containing reducing gas.
- the oxygen capacity at 400° C. of the oxygen carrier contained in the reducing agent is preferably 0.1 to 40% by mass, more preferably 0.5 to 30% by mass.
- the oxygen capacity at low temperature of the oxygen carrier contained in the reducing agent is within the above range, it means that the oxygen capacity is sufficiently high even at the temperature during actual operation (temperature above 650 ° C.), and it is one of carbon dioxide. It can be said that it is a reducing agent with extremely high conversion efficiency to carbon oxide.
- the method for producing the reducing agent is not particularly limited, and examples thereof include a sol-gel method, a coprecipitation method, a solid phase method, a hydrothermal synthesis method and the like.
- the reducing agent can be produced as follows. First, an aqueous solution is prepared by dissolving a salt of a metal element that constitutes a reducing agent (when using the inorganic binder, the salt of the element that constitutes the inorganic binder may be included) in water. Then, after gelling the aqueous solution, it is dried and baked.
- the reducing agent of the present invention can be easily and reliably produced by the so-called sol-gel method.
- acidic water adjusted to be acidic with citric acid, acetic acid, malic acid, tartaric acid, hydrochloric acid, nitric acid, or a mixture thereof may be used.
- salts of metal elements include nitrates, sulfates, chlorides, hydroxides, carbonates, and composites thereof. Of these, nitrates are preferred. Moreover, you may use a hydrate for the salt of a metal element as needed.
- the gel is dried at a temperature of preferably 20° C. to 200° C., more preferably 50° C. to 150° C., preferably 0.5 hours to 20 hours, more preferably 1 hour to 15 hours. do it. By drying in this manner, the gel can be dried uniformly.
- the gel is baked at a temperature of preferably 300° C. or higher and 1200° C. or lower, more preferably 700° C. or higher and 1000° C. or lower, for preferably 1 hour or more and 24 hours or less, more preferably 1.5 hours or more and 20 hours or less.
- the gel preferably becomes an oxide upon calcination, but can be easily converted to a reducing agent by calcination under the above calcination conditions. Further, if the firing is performed under the above firing conditions, excessive particle growth of the reducing agent can be prevented.
- the temperature should be raised at a rate of 1° C./min to 20° C./min, preferably at a rate of 2° C./min to 10° C./min until the firing temperature is reached. As a result, the growth of the reducing agent particles can be promoted, and cracking of the crystals (particles) can be avoided.
- the reducing agent can be produced as follows. First, oxides containing each of the metal elements constituting the reducing agent are mixed and pulverized. For pulverization, for example, a ball mill, bead mill, jet mill, hammer mill or the like can be used. Also, this pulverization may be carried out either dry or wet. If a binder is used, it is mixed with the oxide. As the binder, an organic binder (organic binder) can be used in addition to the above inorganic binders. Examples of organic substances include various resins such as olefin resins, acrylic resins, styrene resins, ester resins, ether resins, and vinyl resins, various waxes, and various fatty acids.
- organic binder organic binder
- organic substances include various resins such as olefin resins, acrylic resins, styrene resins, ester resins, ether resins, and vinyl resins, various waxes, and various fatty acids.
- the oxides can be the above-described oxides produced using the sol-gel method, coprecipitation method, solid-phase method, hydrothermal synthesis method, or the like.
- the pulverized agglomerates are pulverized and then fired. This calcination is preferably performed at a temperature of 300° C. or higher and 1200° C. or lower, more preferably 700° C. or higher and 1000° C. or lower, for preferably 1 hour or more and 24 hours or less, more preferably 1.5 hours or more and 20 hours or less. do it. At this time, part or all of the organic binder may disappear by firing. Thereafter, the reducing agent can be obtained by pulverizing the fired lumps in the same manner as described above.
- the reducing agent of the present invention can be used, for example, in the chemical looping method, as described above.
- the reducing agent of the present invention can be used for the application of reducing carbon dioxide by contact to produce carbon monoxide (carbon valuables). More specifically, a reduction reaction of carbon dioxide and a reduction reaction of a reducing agent are preferably performed, and the reducing agent is used so as to circulate between the reduction reaction of carbon dioxide and the reduction reaction of the reducing agent. is preferred.
- a reducing gas containing other reducing substances is used in the reduction reaction of the reducing agent.
- the reducing agent of the present invention is preferably used for so-called reverse water gas shift reaction.
- the reverse water gas shift reaction is a reaction that produces carbon monoxide and water from carbon dioxide and hydrogen.
- the reverse water gas shift reaction is divided into a reducing agent reduction reaction (first process) and a carbon dioxide reduction reaction (second process).
- the reaction is represented by the formula (A)
- the reduction reaction of carbon dioxide is represented by the following formula (B).
- x is usually 2. That is, in the reduction reaction of the reducing agent, hydrogen, which is one type of reducing substance, is oxidized to produce water. In addition, in the reduction reaction of carbon dioxide, carbon monoxide, which is a type of carbon valuables, is produced by reducing carbon dioxide.
- the reaction temperature in the reduction reaction of the reducing agent may be any temperature at which the reduction reaction can proceed, but is preferably above 650°C, and is preferably 700°C or higher. is more preferred, 750° C. or higher is even more preferred, and 800° C. or higher is particularly preferred. Within this temperature range, the reduction reaction of the reducing agent can proceed efficiently.
- the upper limit of the reaction temperature is preferably 1050° C. or lower, more preferably 1000° C. or lower, even more preferably 950° C. or lower, particularly preferably 900° C. or lower, and 850° C. or lower. Most preferably there is. By setting the upper limit of the reaction temperature within the above range, economic efficiency can be improved.
- the lower limit and the upper limit can be arbitrarily combined to define the range of the reaction temperature.
- the amount of hydrogen (reducing gas) brought into contact with the reducing agent in an oxidized state is preferably 1 mmol or more and 50 mmol or less, more preferably 2.5 mmol or more and 35 mmol or less, with respect to 1 g of the reducing agent. more preferably 5 mmol or more and 20 mmol or less.
- the reducing agent of the present invention has a high hydrogen utilization rate because the oxygen element enters and exits smoothly. Therefore, the reducing agent of the present invention is sufficiently reduced (regenerated) with a small amount of hydrogen. Therefore, it contributes to the reduction of the energy required for hydrogen production, and thus the reduction of carbon dioxide generated when the energy is obtained.
- the hydrogen utilization rate (%) is the ratio of the amount (number of moles) of generated carbon monoxide to the amount (number of moles) of hydrogen brought into contact with 1 g of the reducing agent, expressed as a percentage.
- a reversible amount of oxygen deficiency is generated in the reducing agent at a predetermined rate.
- This specific ratio is preferably 1.6% or more, more preferably 2% or more, and further preferably 2.5% or more with respect to the mass of the oxygen carrier contained in the reducing agent. preferable.
- the conversion of carbon dioxide to carbon monoxide can be further promoted by creating oxygen defects at such a rate.
- the upper limit of the oxygen deficiency amount is not particularly limited, it is usually about 10%.
- the amount of oxygen deficiency can be determined by the method described in Examples below.
- the reaction temperature (the contact temperature of the reducing agent with carbon dioxide) in the reduction reaction of carbon dioxide is preferably a temperature above 650°C, more preferably 700°C or higher, and 750°C or higher. is more preferable, and 800° C. or higher is particularly preferable.
- An efficient carbon dioxide reduction reaction can proceed within this temperature range.
- the upper limit of the reaction temperature is preferably 1050° C. or lower, more preferably 1000° C. or lower, even more preferably 950° C. or lower, particularly preferably 900° C. or lower, and 850° C. or lower. Most preferably there is. Since the reducing agent can reduce carbon dioxide to carbon monoxide with high efficiency even at low temperatures, the reduction reaction of carbon dioxide can be set to a relatively low temperature. Further, by setting the upper limit of the reaction temperature within the above range, it is possible not only to facilitate utilization of waste heat, but also to further improve economic efficiency. In addition, the lower limit and the upper limit can be arbitrarily combined to define the range of the reaction temperature.
- the amount of carbon dioxide brought into contact with the reducing agent is preferably 1 mmol or more and 50 mmol or less, more preferably 2.5 mmol or more and 30 mmol or less, relative to 1 g of the reducing agent. More preferably, it is 5 mmol or more and 20 mmol or less.
- the reducing agent of the present invention facilitates entry and exit of oxygen element. Therefore, the reducing agent of the present invention has a high conversion efficiency of carbon dioxide to carbon monoxide (that is, a large amount of carbon monoxide is produced), and from this point of view also contributes to the reduction of carbon dioxide.
- the reducing agent can be regenerated with a small amount of hydrogen.
- the amount of carbon monoxide produced in the reducing agent of the present invention is preferably about 0.3 mmol or more and 1 mmol or less per 1 g of the reducing agent.
- the reduced product (carbon valuables) obtained by the reduction reaction of carbon dioxide contains carbon monoxide, but may contain substances other than carbon monoxide, and carbon monoxide and other substances It may be a mixture with Specific examples of other substances include, for example, methane. It is preferable that the reduced product such as carbon monoxide obtained by the carbon dioxide reduction reaction is further converted into an organic substance or the like by microbial fermentation or the like. Microbial fermentation includes anaerobic fermentation. Organic substances obtained include methanol, ethanol, acetic acid, butanol, derivatives thereof, mixtures thereof, and C5 or higher compounds such as isoprene.
- the reduced products such as carbon monoxide may be converted into C1 to C20 compounds including hydrocarbons and alcohols conventionally synthesized by petrochemicals by metal oxides.
- Specific compounds obtained include methane, ethane, propylene, methanol, ethanol, propanol, acetaldehyde, diethyl ether, acetic acid, butyric acid, diethyl carbonate, butadiene, and the like.
- the reducing agent of the present invention preferably has the following properties. That is, when a reducing agent is filled at a height of 40 cm in a stainless steel reaction tube with an inner diameter of 8 mm and a pressure gauge is arranged in the flow channel, and nitrogen gas with a concentration of 100% by volume is passed at 30 mL / min, The pressure rise in 10 minutes is preferably 0.03 MPaG or less, more preferably 0.01 MPaG or less. A reducing agent exhibiting such characteristics can be judged to satisfy the above ranges in packing density and pore volume, and can sufficiently increase the conversion efficiency of carbon dioxide to carbon monoxide.
- the present invention as described above, it is possible to provide a reducing agent that can be used in reactions at high temperatures, and a method for producing gas using this reducing agent. Since the reducing agent of the present invention can withstand use at high temperatures, chemical looping reactions at high temperatures enable more efficient conversion of carbon dioxide to carbon monoxide (carbon value).
- a reducing agent that reduces carbon dioxide by contact to produce carbon valuables is composed of cerium (Ce) and a metal oxide containing a transition element other than cerium (Ce), and has oxygen ion conductivity
- the peak position of at least one diffraction peak corresponding to the (220) plane in the X-ray diffraction profile is that of cerium oxide (CeO 2 )
- the diffraction peak corresponding to the (220) plane of the oxygen carrier with respect to the peak position of the diffraction peak corresponding to the (220) plane of the cerium oxide (CeO 2 )
- the amount of shift of the peak position of is 0.1° or more and less than 0.6° in 2 ⁇ .
- the transition element is at least one element belonging to the fourth period and the fifth period of the periodic table. reducing agent.
- Ce cerium
- Ce metal oxide containing a transition element other than cerium
- the method for producing a reducing agent and gas of the present invention may have any other configuration added to the above embodiments, and may be replaced with any configuration that performs similar functions. Well, part of the configuration may be omitted.
- a gas containing hydrogen was described as a representative example of the reducing gas.
- the reducing gas includes a hydrocarbon (eg, methane, ethane, acetylene, etc.) as a reducing substance instead of or in addition to hydrogen. and ammonia can also be used.
- Example 1 Production of reducing agent (Example 1) First, cerium oxide (manufactured by Kojundo Chemical Co., Ltd.), manganese (IV) oxide (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), and iron oxide (III) (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) were weighed out in predetermined amounts. Next, the weighed particles of each oxide, 100 mL of deionized water, and zirconia beads of 4 mm ⁇ were placed in a zirconia container. After that, they were pulverized with zirconia beads at a rotation speed of 400 rpm for 24 hours, and then dried at 120°C. The molar ratio of cerium oxide, manganese oxide and iron oxide was 0.94:0.04:0.02.
- the resulting oxide mass was pulverized, heated from room temperature to 450°C at a rate of 8°C/min in an air atmosphere, and then fired at 450°C for 4 hours. After that, the temperature was further raised to 950° C. at a rate of 8° C./min, and then fired at 950° C. for 8 hours. Finally, the calcined mass was finely ground mechanically. As a result, the desired reducing agent composed solely of the oxygen carrier was obtained. The reducing agent was granular.
- Example 2 A reducing agent was produced in the same manner as in Example 1, except that the 24-hour pulverization was changed to 20-hour pulverization.
- Example 3 First, as precursors of the reducing agent, cerium (III) nitrate hexahydrate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., purity: 98.0%) and zirconium nitrate dihydrate (FUJIFILM Wako Pure Chemical Industries, Ltd.
- citric acid manufactured by Fuji Film Wako Pure Chemical Industries, Ltd., purity: 99.5%
- aqueous citric acid solution 6.06 g was weighed and dissolved in 96 mL of deionized water to obtain an aqueous citric acid solution.
- the above precursor metal nitrate
- the Ce:Zr+Sm+Fe+Cu (molar ratio) in the precursor aqueous solution was set to 0.70:0.30.
- ethylene glycol manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purity: 99.5%
- ethylene glycol manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purity: 99.5%
- a temperature of 80° C. was maintained with continuous stirring until a viscous gel was formed. After that, the gel was transferred to a drying oven. Drying of the gel was performed at 120° C. for 5 hours. The resulting swollen lumps of organic and inorganic compounds were pulverized, heated from room temperature to 450° C. at a rate of 8° C./min, and then calcined at 450° C. for 4 hours. After that, the temperature was further raised to 950° C. at a rate of 8° C./min, and then fired at 950° C. for 8 hours. Finally, the calcined mass was finely ground mechanically. As a result, the desired reducing agent composed solely of the oxygen carrier was obtained. The reducing agent was granular.
- Example 4 A reducing agent was produced in the same manner as in Example 3, except that the type of precursor of the reducing agent was changed.
- precursors of the reducing agent cerium (III) nitrate hexahydrate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., purity: 98.0%) and zirconium nitrate dihydrate (FUJIFILM Wako Pure Chemical Industries, Ltd.
- Example 5 A reducing agent was produced in the same manner as in Example 3, except that the type of precursor of the reducing agent was changed.
- precursors of the reducing agent cerium (III) nitrate hexahydrate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., purity: 98.0%) and zirconium nitrate dihydrate (FUJIFILM Wako Pure Chemical Industries, Ltd. company, purity: 97.0%) and nickel (II) nitrate hexahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purity: 99.9%) were weighed in predetermined amounts.
- the Ce:Zr:Ni (molar ratio) in the precursor aqueous solution was set to 0.90:0.08:0.02.
- Example 6 A reducing agent was produced in the same manner as in Example 3, except that the type of precursor of the reducing agent was changed.
- precursors of the reducing agent cerium (III) nitrate hexahydrate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., purity: 98.0%) and zirconium nitrate dihydrate (FUJIFILM Wako Pure Chemical Industries, Ltd.
- Predetermined amounts of ammonium niobium oxalate (Sigma-Aldrich, purity: 97.0%) and niobium ammonium oxalate (purity: 99.99%) were weighed.
- the Ce:Zr:Nb (molar ratio) in the precursor aqueous solution was set to 0.90:0.08:0.02.
- Example 7 A reducing agent was produced in the same manner as in Example 3, except that the type of precursor of the reducing agent was changed.
- precursors of the reducing agent cerium (III) nitrate hexahydrate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., purity: 98.0%) and 30% titanium (IV) sulfate solution (FUJIFILM Wako Pure Chemical Industries, Ltd. Kogyo Co., Ltd.) and lanthanum (III) nitrate hexahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purity: 99.9%) were weighed in predetermined amounts.
- the Ce:Ti:La (molar ratio) in the precursor aqueous solution was set to 0.58:0.25:0.17.
- Example 8 Aluminum oxide (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd., special grade Wako) was weighed as a binder to the oxygen carrier obtained in Example 3, and mixed in a mortar for 10 minutes. After that, the temperature was raised from room temperature to 950° C. at a rate of 8° C./min in an air atmosphere, and then fired at 950° C. for 8 hours. Thus, a reducing agent was obtained. The ratio of aluminum oxide contained in the reducing agent was 10 parts by mass with respect to 100 parts by mass of the reducing agent.
- Comparative example 1 A reducing agent was obtained by tableting cerium oxide alone.
- the packing densities of the reducing agents obtained in Examples 1 to 3 were 2 g/mL or more and 2.5 g/mL or less.
- the metal composition in the reducing agent (metal oxide) was analyzed and identified by ICP emission spectrometry using argon gas using SPECTRO ARCOS manufactured by AMETEK.
- a measurement solution was prepared by the following method. 50 to 100 mg of a reducing agent was dissolved in 100 mL of 1% nitric acid to 1% hydrofluoric acid, and the obtained solution was further diluted 10 times. Table 1 shows the results (molar ratios of metal elements) of the analysis of the measurement solution.
- the particle size distribution of the reducing agent was measured using a particle size distribution analyzer ("LA-960S" manufactured by Horiba, Ltd.). Water was used as a solvent, and the measurement was performed in a state where the transmittance was 70% or more. As a result, the volume-based 50% diameters of the reducing agents were all 50 ⁇ m or less.
- a reducing agent sample was prepared. First, about 100 mg of reducing agent was weighed into a mortar and ground with a pestle. After that, the reducing agent was uniformly filled into the holes of the sample filling portion of the sample plate, and the surface of the sample plate and the surface of the reducing agent were adjusted to be flush with each other. For the X-ray diffraction measurement, an X-ray diffractometer ("D8 DISCOVER" manufactured by Bruker Co., Ltd.) was used, and the measurement was performed by the concentration method.
- D8 DISCOVER manufactured by Bruker Co., Ltd.
- the diffractometer was set with a divergence slit of 1/2°, a divergence longitudinal limiting slit of 10 mm, a scattering slit of 2°, and a receiving slit of 0.15 mm.
- the goniometer radius was 169.3 mm.
- the prepared reducing agent sample was irradiated with X-rays.
- the scanning angle of the goniometer was set in the range of 5.5 to 100.5°, the scanning speed was set at 3.5°/min, and the measurement step was set at 0.01. Measurements were performed at room temperature in air. After the measurement was completed, data obtained without separating K ⁇ 1 and K ⁇ 2 were analyzed. Software (DIFFRAC.EVA manufactured by Bruker) was used for data analysis. After removing the background, the highest value of the diffraction peak intensity corresponding to the (220) plane was taken as the peak, and the angle of the peak at this time was taken as the peak position.
- the full width at half maximum was defined as the interval between the two points at half the intensity of the maximum peak value.
- the ratio of the peak intensity to the full width at half maximum was calculated using the peak intensity (unit: cps) after background removal.
- D is the crystallite size ( ⁇ )
- ⁇ is the measured X-ray wavelength ( ⁇ )
- ⁇ is the broadening of the diffraction line width due to the crystallite size
- ⁇ is the diffraction angle
- K is the Scherrer's constant
- B obs is the measured half-width
- b is the instrumental linewidth broadening.
- K was calculated as 0.890 and b as 0.050.
- Amount of carbon monoxide produced (amount of CO produced)
- a quartz reaction tube having an inner diameter of 4 mm was prepared and filled with a cylindrical reducing agent formed to have a long diameter of 3 mm so that the layer height was 30 mm.
- the amount of carbon monoxide produced is from 0.001 mmol or more per second to 0.001 mmol or less. It was defined as a value obtained by dividing the total amount of carbon monoxide produced by the weight (g) of the reducing agent.
- the ⁇ S part (detection part) was used after being calibrated under the following conditions. That is, using a mass flow controller calibrated with carbon dioxide, with a discharge full scale of 10 mL / min or 50 mL / min, a flow rate accuracy of ⁇ 1.0%, and a repeatability of ⁇ 0.2%, carbon dioxide is Plot the detected signal intensity when flowing at 2, 3 mL / min, and use the least squares method to approximate the calibration curve with a straight line passing through the origin . Signal strength was adjusted. Based on this, the detected amount (the amount of carbon dioxide produced per second) was calculated with respect to the detected signal intensity of carbon dioxide. Also, carbon monoxide was similarly calibrated by the following procedure.
- the peak position of the diffraction peak corresponding to the (220) plane, its full width at half maximum, crystallite size, peak intensity/full width at half maximum, and the amount of carbon monoxide produced are shown in Table 1 below.
- the reducing agent of each example produced a larger amount of carbon monoxide than the reducing agent of Comparative Example 1, which was cerium oxide alone.
- Amount of Oxygen Deficit The amount of oxygen vacancy of the reducing agents obtained in Example 1 and Comparative Example 1 was measured using thermogravimetry (TG). The difference between the mass reduced by the reducing agent hydrogen and the mass increased by carbon dioxide is divided by the mass of the oxygen carrier contained in the charged reducing agent. , 100 to obtain the amount of oxygen deficiency (%). Specifically, first, a sample container was filled with 100 mg of a reducing agent. Next, the temperature was raised to 850° C. or 650° C. at 10° C./min while flowing helium.
- a mixed gas of hydrogen and helium (10% by volume of hydrogen) was flowed at 100 mL/min for 10 minutes to reduce the reducing agent. After 10 minutes, helium gas was flowed at 100 mL/min for 30 minutes for gas exchange. The weight of the reducing agent at this time is defined as "A”.
- a mixed gas of carbon dioxide and helium (10% by volume of carbon dioxide) was flowed at 100 mL/min for 10 minutes to oxidize the reducing agent. After 10 minutes, helium gas was flowed at 100 mL/min for 30 minutes for gas exchange. The weight of the reducing agent at this time is defined as "B”.
- the amount of oxygen deficiency (%) was determined by (BA/mass of oxygen carrier contained in reducing agent) ⁇ 100.
- the oxygen carrier contained in the reducing agent of each example had a larger amount of oxygen deficiency than the cerium oxide alone constituting the reducing agent of Comparative Example 1. This result is in good agreement with the high conversion efficiency of carbon dioxide to carbon monoxide.
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Abstract
[Problem] To provide a reducing agent which can be used in a reaction at a high temperature, and a gas production method in which the reducing agent is used. [Solution] According to one aspect of the present invention, provided is a reducing agent that reduces carbon dioxide through contact to produce a valuable carbon substance. The reducing agent is composed of cerium (Ce) and a metal oxide containing a transition element other than cerium (Ce), and contains an oxygen carrier having oxygen ion conductivity. When the oxygen carrier is subjected to an X-ray diffraction measurement, a peak position of at least one diffraction peak corresponding to the (220) plane in the X-ray diffraction profile is shifted relative to a peak position of the diffraction peak corresponding to the (220) plane of a cerium oxide (CeO2).
Description
本発明は、還元剤およびガスの製造方法に関し、より詳しくは、例えば、ケミカルルーピング法に利用可能な還元剤、およびかかる還元剤を使用したガスの製造方法に関する。
The present invention relates to a reducing agent and a method for producing a gas, and more particularly to a reducing agent that can be used in chemical looping, and a method for producing a gas using such a reducing agent.
近年、温室効果ガスの一種である二酸化炭素は、その大気中の濃度が上昇を続けている。大気中の二酸化炭素の濃度の上昇は、地球温暖化を助長する。したがって、大気中に放出される二酸化炭素を回収することは重要であり、さらに回収した二酸化炭素を有価物質に変換して再利用できれば、炭素循環社会を実現することができる。
従来、二酸化炭素から一酸化炭素を製造する方法として、逆水性ガスシフト反応を利用した方法が知られている。しかしながら、この従来の逆水性ガスシフト反応は、生成物である一酸化炭素と水とが系内に共存するため、化学平衡の制約により二酸化炭素の一酸化炭素への変換効率が低くなるという点で問題があった。 In recent years, the atmospheric concentration of carbon dioxide, which is a kind of greenhouse gas, continues to rise. Rising concentrations of carbon dioxide in the atmosphere contribute to global warming. Therefore, it is important to recover the carbon dioxide released into the atmosphere, and if the recovered carbon dioxide can be converted into a valuable substance and reused, a carbon recycling society can be realized.
Conventionally, as a method for producing carbon monoxide from carbon dioxide, a method using a reverse water gas shift reaction is known. However, in this conventional reverse water gas shift reaction, the product carbon monoxide and water coexist in the system, so the efficiency of converting carbon dioxide to carbon monoxide is low due to chemical equilibrium restrictions. I had a problem.
従来、二酸化炭素から一酸化炭素を製造する方法として、逆水性ガスシフト反応を利用した方法が知られている。しかしながら、この従来の逆水性ガスシフト反応は、生成物である一酸化炭素と水とが系内に共存するため、化学平衡の制約により二酸化炭素の一酸化炭素への変換効率が低くなるという点で問題があった。 In recent years, the atmospheric concentration of carbon dioxide, which is a kind of greenhouse gas, continues to rise. Rising concentrations of carbon dioxide in the atmosphere contribute to global warming. Therefore, it is important to recover the carbon dioxide released into the atmosphere, and if the recovered carbon dioxide can be converted into a valuable substance and reused, a carbon recycling society can be realized.
Conventionally, as a method for producing carbon monoxide from carbon dioxide, a method using a reverse water gas shift reaction is known. However, in this conventional reverse water gas shift reaction, the product carbon monoxide and water coexist in the system, so the efficiency of converting carbon dioxide to carbon monoxide is low due to chemical equilibrium restrictions. I had a problem.
そこで、上記問題を解決するため、ケミカルルーピング法を利用して二酸化炭素から一酸化炭素の変換（合成）が行われる。ここで言うケミカルルーピング法とは、上記逆水性ガスシフト反応を、水素による還元反応と、二酸化炭素からの一酸化炭素の生成反応との２つの反応に分割し、これらの反応を酸素キャリア（例えば、金属酸化物：ＭＯｘ）によって橋渡しさせるという方法である（下記式参照）。
Ｈ２ ＋ ＭＯｘ → Ｈ２Ｏ ＋ ＭＯｘ－１
ＣＯ２ ＋ ＭＯｘ－１ → ＣＯ ＋ ＭＯｘ
なお、上記式中、ＭＯｘ－１は、金属酸化物の一部または全部が還元された状態を示す。 Therefore, in order to solve the above problem, a chemical looping method is used to convert (synthesize) carbon monoxide from carbon dioxide. The chemical looping method referred to here divides the reverse water gas shift reaction into two reactions, a reduction reaction with hydrogen and a reaction of producing carbon monoxide from carbon dioxide, and divides these reactions into oxygen carrier (for example, It is a method of bridging with a metal oxide: MO x ) (see the formula below).
H 2 + MO x → H 2 O + MO x−1
CO 2 + MO x-1 → CO + MO x
In the above formula, MO x-1 represents a state in which part or all of the metal oxide has been reduced.
Ｈ２ ＋ ＭＯｘ → Ｈ２Ｏ ＋ ＭＯｘ－１
ＣＯ２ ＋ ＭＯｘ－１ → ＣＯ ＋ ＭＯｘ
なお、上記式中、ＭＯｘ－１は、金属酸化物の一部または全部が還元された状態を示す。 Therefore, in order to solve the above problem, a chemical looping method is used to convert (synthesize) carbon monoxide from carbon dioxide. The chemical looping method referred to here divides the reverse water gas shift reaction into two reactions, a reduction reaction with hydrogen and a reaction of producing carbon monoxide from carbon dioxide, and divides these reactions into oxygen carrier (for example, It is a method of bridging with a metal oxide: MO x ) (see the formula below).
H 2 + MO x → H 2 O + MO x−1
CO 2 + MO x-1 → CO + MO x
In the above formula, MO x-1 represents a state in which part or all of the metal oxide has been reduced.
かかるケミカルルーピング法では、それぞれの反応時には、逆反応の基質である水および一酸化炭素が共存しないため、逆水性ガスシフト反応の化学平衡よりも高い二酸化炭素の一酸化炭素への変換効率を得られる可能性がある。
このケミカルルーピング法では、従来、酸素キャリアに形成された酸素欠損を介して、二酸化炭素を一酸化炭素へ変換する反応を６５０℃以下の温度条件で行っている（特許文献１参照）。 In such a chemical looping method, water and carbon monoxide, which are substrates for the reverse reaction, do not coexist during each reaction, so that conversion efficiency of carbon dioxide to carbon monoxide higher than that in the chemical equilibrium of the reverse water-gas shift reaction can be obtained. there is a possibility.
In this chemical looping method, conventionally, the reaction of converting carbon dioxide into carbon monoxide via oxygen vacancies formed in oxygen carriers is carried out at a temperature of 650° C. or less (see Patent Document 1).
このケミカルルーピング法では、従来、酸素キャリアに形成された酸素欠損を介して、二酸化炭素を一酸化炭素へ変換する反応を６５０℃以下の温度条件で行っている（特許文献１参照）。 In such a chemical looping method, water and carbon monoxide, which are substrates for the reverse reaction, do not coexist during each reaction, so that conversion efficiency of carbon dioxide to carbon monoxide higher than that in the chemical equilibrium of the reverse water-gas shift reaction can be obtained. there is a possibility.
In this chemical looping method, conventionally, the reaction of converting carbon dioxide into carbon monoxide via oxygen vacancies formed in oxygen carriers is carried out at a temperature of 650° C. or less (see Patent Document 1).
本発明者らの検討によれば、水素により酸素キャリアの結晶構造中に酸素欠損を生じさせる反応は吸熱反応であるため、この酸素欠損を効率よく生成させるためには、上記反応をより高温で行うのがよいことが判明した。しかしながら、これまで、酸素欠損を生じさせる反応の高温領域（６５０℃を上回る温度）での検討は不十分であった。
本発明では上記事情に鑑み、高温での反応に使用可能な還元剤、およびかかる還元剤を使用したガスの製造方法を提供することとした。 According to studies by the present inventors, the reaction in which hydrogen causes oxygen vacancies in the crystal structure of the oxygen carrier is an endothermic reaction. It turned out to be a good thing to do. However, until now, investigations in the high temperature range (temperature above 650° C.) of the reaction that causes oxygen deficiency have been insufficient.
In view of the above circumstances, the present invention provides a reducing agent that can be used in reactions at high temperatures, and a method for producing gas using such a reducing agent.
本発明では上記事情に鑑み、高温での反応に使用可能な還元剤、およびかかる還元剤を使用したガスの製造方法を提供することとした。 According to studies by the present inventors, the reaction in which hydrogen causes oxygen vacancies in the crystal structure of the oxygen carrier is an endothermic reaction. It turned out to be a good thing to do. However, until now, investigations in the high temperature range (temperature above 650° C.) of the reaction that causes oxygen deficiency have been insufficient.
In view of the above circumstances, the present invention provides a reducing agent that can be used in reactions at high temperatures, and a method for producing gas using such a reducing agent.
本発明の一態様によれば、接触により二酸化炭素を還元して炭素有価物を生成する還元剤が提供される。この還元剤は、セリウム（Ｃｅ）およびセリウム（Ｃｅ）以外の遷移元素を含む金属酸化物で構成され、酸素イオン伝導性を備える酸素キャリアを含有する。酸素キャリアのＸ線回折測定を行ったとき、Ｘ線回折プロファイルにおいて、（２２０）面に対応する少なくとも１つの回折ピークのピーク位置が、酸化セリウム（ＣｅＯ２）の（２２０）面に対応する回折ピークのピーク位置に対してシフトしている。
According to one aspect of the present invention, a reducing agent is provided that reduces carbon dioxide upon contact to produce a carbon value. This reducing agent is composed of metal oxides containing cerium (Ce) and transition elements other than cerium (Ce), and contains an oxygen carrier with oxygen ion conductivity. When the X-ray diffraction measurement of the oxygen carrier is performed, the peak position of at least one diffraction peak corresponding to the (220) plane in the X-ray diffraction profile corresponds to the (220) plane of cerium oxide (CeO 2 ). The peak is shifted with respect to the peak position.
かかる態様によれば、高温での反応に使用可能な還元剤を得ることができる。
According to this aspect, it is possible to obtain a reducing agent that can be used for reactions at high temperatures.
以下、本発明の還元剤およびガスの製造方法について、好適実施形態に基づいて詳細に説明する。
［還元剤］
本発明の還元剤は、二酸化炭素を含む原料ガスを還元剤と接触させることにより、二酸化炭素を還元して一酸化炭素（炭素有価物）を含む生成ガスを製造する際に使用される（すなわち、本発明のガスの製造方法に使用される）。また、二酸化炭素との接触により酸化された還元剤は、水素（還元物質）を含む還元ガスと接触させることにより還元（再生）され得る。
この際、好ましくは、本発明の還元剤を充填した反応管（反応容器）内に、原料ガスおよび還元ガスを交互に通過させることにより、還元剤による二酸化炭素の一酸化炭素への変換と、還元ガスによる酸化状態の還元剤の再生とが行われる。 BEST MODE FOR CARRYING OUT THE INVENTION A method for producing a reducing agent and a gas according to the present invention will be described in detail below based on preferred embodiments.
[Reducing agent]
The reducing agent of the present invention is used in producing a product gas containing carbon monoxide (carbon value) by reducing carbon dioxide by contacting a raw material gas containing carbon dioxide with the reducing agent (i.e. , used in the gas production method of the present invention). Also, the reducing agent oxidized by contact with carbon dioxide can be reduced (regenerated) by contact with a reducing gas containing hydrogen (reducing substance).
At this time, preferably, a raw material gas and a reducing gas are alternately passed through a reaction tube (reaction vessel) filled with the reducing agent of the present invention, thereby converting carbon dioxide into carbon monoxide by the reducing agent, Regeneration of the reducing agent in an oxidized state by the reducing gas is performed.
［還元剤］
本発明の還元剤は、二酸化炭素を含む原料ガスを還元剤と接触させることにより、二酸化炭素を還元して一酸化炭素（炭素有価物）を含む生成ガスを製造する際に使用される（すなわち、本発明のガスの製造方法に使用される）。また、二酸化炭素との接触により酸化された還元剤は、水素（還元物質）を含む還元ガスと接触させることにより還元（再生）され得る。
この際、好ましくは、本発明の還元剤を充填した反応管（反応容器）内に、原料ガスおよび還元ガスを交互に通過させることにより、還元剤による二酸化炭素の一酸化炭素への変換と、還元ガスによる酸化状態の還元剤の再生とが行われる。 BEST MODE FOR CARRYING OUT THE INVENTION A method for producing a reducing agent and a gas according to the present invention will be described in detail below based on preferred embodiments.
[Reducing agent]
The reducing agent of the present invention is used in producing a product gas containing carbon monoxide (carbon value) by reducing carbon dioxide by contacting a raw material gas containing carbon dioxide with the reducing agent (i.e. , used in the gas production method of the present invention). Also, the reducing agent oxidized by contact with carbon dioxide can be reduced (regenerated) by contact with a reducing gas containing hydrogen (reducing substance).
At this time, preferably, a raw material gas and a reducing gas are alternately passed through a reaction tube (reaction vessel) filled with the reducing agent of the present invention, thereby converting carbon dioxide into carbon monoxide by the reducing agent, Regeneration of the reducing agent in an oxidized state by the reducing gas is performed.
本発明の還元剤は、酸素イオン伝導性を備える酸素キャリアを含有する。
ここで、酸素キャリアとは、可逆的な酸素欠損を生じ得る化合物であり、それ自体から還元により酸素元素が欠損するが、酸素元素が欠損した状態（還元状態）で、二酸化炭素と接触すると、二酸化炭素から酸素元素を奪い取って還元する作用を示す化合物のことを言う。
本発明における酸素キャリアは、セリウム（Ｃｅ）およびセリウム（Ｃｅ）以外の遷移元素を含む金属酸化物で構成されている。かかる酸素キャリアでは、Ｃｅと遷移元素との相乗効果により、二酸化炭素からの一酸化炭素の生成が促進される。 The reducing agent of the present invention contains an oxygen carrier with oxygen ion conductivity.
Here, the oxygen carrier is a compound that can cause reversible oxygen deficiency, and the oxygen element itself is deficient due to reduction. It refers to a compound that shows the action of depriving carbon dioxide of oxygen element and reducing it.
The oxygen carrier in the present invention is composed of cerium (Ce) and a metal oxide containing a transition element other than cerium (Ce). In such an oxygen carrier, the synergistic effect of Ce and the transition element promotes the production of carbon monoxide from carbon dioxide.
ここで、酸素キャリアとは、可逆的な酸素欠損を生じ得る化合物であり、それ自体から還元により酸素元素が欠損するが、酸素元素が欠損した状態（還元状態）で、二酸化炭素と接触すると、二酸化炭素から酸素元素を奪い取って還元する作用を示す化合物のことを言う。
本発明における酸素キャリアは、セリウム（Ｃｅ）およびセリウム（Ｃｅ）以外の遷移元素を含む金属酸化物で構成されている。かかる酸素キャリアでは、Ｃｅと遷移元素との相乗効果により、二酸化炭素からの一酸化炭素の生成が促進される。 The reducing agent of the present invention contains an oxygen carrier with oxygen ion conductivity.
Here, the oxygen carrier is a compound that can cause reversible oxygen deficiency, and the oxygen element itself is deficient due to reduction. It refers to a compound that shows the action of depriving carbon dioxide of oxygen element and reducing it.
The oxygen carrier in the present invention is composed of cerium (Ce) and a metal oxide containing a transition element other than cerium (Ce). In such an oxygen carrier, the synergistic effect of Ce and the transition element promotes the production of carbon monoxide from carbon dioxide.
本発明では、酸素キャリアのＸ線回折測定を行ったとき、Ｘ線回折プロファイルにおいて、（２２０）面に対応する少なくとも１つの回折ピークのピーク位置が、酸化セリウム（ＣｅＯ２）の（２２０）面に対応する回折ピークのピーク位置に対してシフトしている。すなわち、酸素キャリアおよび酸化セリウムに対して同じ条件でＸ線回折測定を行ったとき、Ｘ線回折プロファイルにおいて、酸素キャリアの（２２０）面に対応する少なくとも１つの回折ピークのピーク位置が、酸化セリウムの（２２０）面に対応する回折ピークのピーク位置に対してシフトしている。なお、Ｘ線回折測定のタイミングは、還元剤をガスとの反応に使用する前、すなわち還元剤の製造直後とされる。
In the present invention, when the X-ray diffraction measurement of the oxygen carrier is performed, the peak position of at least one diffraction peak corresponding to the (220) plane in the X-ray diffraction profile is the (220) plane of cerium oxide (CeO 2 ). are shifted with respect to the peak positions of the diffraction peaks corresponding to . That is, when X-ray diffraction measurement is performed under the same conditions for the oxygen carrier and cerium oxide, the peak position of at least one diffraction peak corresponding to the (220) plane of the oxygen carrier in the X-ray diffraction profile is the same as that of the cerium oxide. is shifted with respect to the peak position of the diffraction peak corresponding to the (220) plane of . The timing of the X-ray diffraction measurement is before the reducing agent is used for the reaction with the gas, that is, immediately after the reducing agent is produced.
このように、Ｘ線回折プロファイルにおいて、（２２０）面に対応する特定の回折ピークのピークシフトが生じている場合、酸化セリウムの結晶にＣｅ以外の遷移元素が十分に固溶していることを示している。
酸化セリウムの結晶にＣｅ以外の遷移元素が十分に固溶することにより、酸化セリウム（酸素キャリア）の結晶構造を適度に歪ませることができる。このため、酸素キャリア内での酸素元素（酸素イオン）の移動度を高めることができ、よって、酸素キャリア（還元剤）は、還元ガスとの接触により酸素元素が効率よく離脱して、酸素欠損が円滑に誘発されるとともに、この誘発された酸素欠損により、二酸化炭素から酸素元素を奪い取り易くなるものと考えられる。 Thus, in the X-ray diffraction profile, when a specific diffraction peak corresponding to the (220) plane is shifted, it means that transition elements other than Ce are sufficiently dissolved in the cerium oxide crystal. showing.
The crystal structure of cerium oxide (oxygen carrier) can be moderately distorted by sufficiently dissolving transition elements other than Ce in the cerium oxide crystal. Therefore, the mobility of the oxygen element (oxygen ion) in the oxygen carrier can be increased, and therefore, the oxygen carrier (reducing agent) efficiently desorbs the oxygen element by contact with the reducing gas, resulting in oxygen deficiency. is smoothly induced, and the induced oxygen deficiency is thought to make it easier to deprive carbon dioxide of oxygen elements.
酸化セリウムの結晶にＣｅ以外の遷移元素が十分に固溶することにより、酸化セリウム（酸素キャリア）の結晶構造を適度に歪ませることができる。このため、酸素キャリア内での酸素元素（酸素イオン）の移動度を高めることができ、よって、酸素キャリア（還元剤）は、還元ガスとの接触により酸素元素が効率よく離脱して、酸素欠損が円滑に誘発されるとともに、この誘発された酸素欠損により、二酸化炭素から酸素元素を奪い取り易くなるものと考えられる。 Thus, in the X-ray diffraction profile, when a specific diffraction peak corresponding to the (220) plane is shifted, it means that transition elements other than Ce are sufficiently dissolved in the cerium oxide crystal. showing.
The crystal structure of cerium oxide (oxygen carrier) can be moderately distorted by sufficiently dissolving transition elements other than Ce in the cerium oxide crystal. Therefore, the mobility of the oxygen element (oxygen ion) in the oxygen carrier can be increased, and therefore, the oxygen carrier (reducing agent) efficiently desorbs the oxygen element by contact with the reducing gas, resulting in oxygen deficiency. is smoothly induced, and the induced oxygen deficiency is thought to make it easier to deprive carbon dioxide of oxygen elements.
また、酸化セリウムの結晶は、Ｃｅ以外の遷移元素が固溶することにより、その結晶構造が安定化して耐熱温度が向上するとも考えられる。その結果、本発明の還元剤は、６５０℃を上回る高温においても使用することができるようになる。
さらに、酸化セリウムの結晶にＣｅ以外の遷移元素が固溶している場合、６５０℃以下で使用するよりも、６５０℃を上回る高温で使用することで、その結晶構造がより安定すると考えられる。６５０℃を上回る高温ではＣｅは遷移金属と合金化し、安定した結晶構造をとり易いため、還元剤の酸化還元を繰り返しても初期活性を維持し易い。 It is also considered that the crystal structure of the cerium oxide crystal is stabilized by solid solution of the transition elements other than Ce, and the heat resistance temperature is improved. As a result, the reducing agents of the present invention can be used even at high temperatures above 650°C.
Furthermore, when transition elements other than Ce are dissolved in cerium oxide crystals, the crystal structure is considered to be more stable when used at a temperature higher than 650°C rather than when used at 650°C or lower. At high temperatures above 650° C., Ce is alloyed with transition metals and tends to form a stable crystal structure, so that initial activity can be easily maintained even after repeated oxidation-reduction of the reducing agent.
さらに、酸化セリウムの結晶にＣｅ以外の遷移元素が固溶している場合、６５０℃以下で使用するよりも、６５０℃を上回る高温で使用することで、その結晶構造がより安定すると考えられる。６５０℃を上回る高温ではＣｅは遷移金属と合金化し、安定した結晶構造をとり易いため、還元剤の酸化還元を繰り返しても初期活性を維持し易い。 It is also considered that the crystal structure of the cerium oxide crystal is stabilized by solid solution of the transition elements other than Ce, and the heat resistance temperature is improved. As a result, the reducing agents of the present invention can be used even at high temperatures above 650°C.
Furthermore, when transition elements other than Ce are dissolved in cerium oxide crystals, the crystal structure is considered to be more stable when used at a temperature higher than 650°C rather than when used at 650°C or lower. At high temperatures above 650° C., Ce is alloyed with transition metals and tends to form a stable crystal structure, so that initial activity can be easily maintained even after repeated oxidation-reduction of the reducing agent.
なお、酸素キャリアの（２２０）面に対応する回折ピークは、酸化セリウム（ＣｅＯ２）の（２２０）面に対応する回折ピークに対して、高角側または低角側のいずれの方向にシフトしていてもよい。酸素キャリアの（２２０）面に対応する回折ピークが高角側または低角側のいずれの方向にシフトするか、あるいはそのシフト量は、例えば、還元剤を製造する際の条件（特に、粉砕時間や、焼成温度および焼成時間）に影響を受けると考えられる。
酸化セリウム（ＣｅＯ２）の（２２０）面に対応する回折ピークのピーク位置に対する、酸素キャリアの（２２０）面に対応する回折ピークのピーク位置のシフト量は、２θで０．１°以上０．６°未満であることが好ましい。ピーク位置のシフト量の下限値は、２θで０．１５°以上、０．２°以上、０．２５°以上、０．３°以上、０．３５°以上、０．４°以上であってもよい。一方、ピーク位置のシフト量の上限値は、２θで０．５５°以下であってもよい。なお、下限値と上限値とは、任意に組み合わせて、ピーク位置のシフト量の好ましい範囲を規定することができる。ピーク位置のシフト量を上記範囲とすることにより、酸化セリウムの結晶にＣｅ以外の遷移元素がより十分かつ確実に固溶していると考えることができる。
なお、ピーク位置のシフト量が大きくなり過ぎると、酸化セリウムの結晶構造である蛍石構造が維持されない可能性がある。 Note that the diffraction peak corresponding to the (220) plane of the oxygen carrier is shifted to either the high angle side or the low angle side with respect to the diffraction peak corresponding to the (220) plane of cerium oxide (CeO 2 ). may Whether the diffraction peak corresponding to the (220) plane of the oxygen carrier shifts to the high-angle side or the low-angle side, or the amount of shift depends, for example, on the conditions for producing the reducing agent (in particular, pulverization time and , firing temperature and firing time).
The shift amount of the peak position of the diffraction peak corresponding to the (220) plane of the oxygen carrier with respect to the peak position of the diffraction peak corresponding to the (220) plane of cerium oxide (CeO 2 ) is 0.1° or more in 2θ and 0.1° or more. It is preferably less than 6°. The lower limit of the shift amount of the peak position is 0.15° or more, 0.2° or more, 0.25° or more, 0.3° or more, 0.35° or more, 0.4° or more in 2θ. good too. On the other hand, the upper limit of the shift amount of the peak position may be 0.55° or less in 2θ. The lower limit value and the upper limit value can be arbitrarily combined to define a preferable range of the shift amount of the peak position. By setting the shift amount of the peak position within the above range, it can be considered that transition elements other than Ce are more sufficiently and reliably dissolved in the cerium oxide crystal.
If the shift amount of the peak position becomes too large, the fluorite structure, which is the crystal structure of cerium oxide, may not be maintained.
酸化セリウム（ＣｅＯ２）の（２２０）面に対応する回折ピークのピーク位置に対する、酸素キャリアの（２２０）面に対応する回折ピークのピーク位置のシフト量は、２θで０．１°以上０．６°未満であることが好ましい。ピーク位置のシフト量の下限値は、２θで０．１５°以上、０．２°以上、０．２５°以上、０．３°以上、０．３５°以上、０．４°以上であってもよい。一方、ピーク位置のシフト量の上限値は、２θで０．５５°以下であってもよい。なお、下限値と上限値とは、任意に組み合わせて、ピーク位置のシフト量の好ましい範囲を規定することができる。ピーク位置のシフト量を上記範囲とすることにより、酸化セリウムの結晶にＣｅ以外の遷移元素がより十分かつ確実に固溶していると考えることができる。
なお、ピーク位置のシフト量が大きくなり過ぎると、酸化セリウムの結晶構造である蛍石構造が維持されない可能性がある。 Note that the diffraction peak corresponding to the (220) plane of the oxygen carrier is shifted to either the high angle side or the low angle side with respect to the diffraction peak corresponding to the (220) plane of cerium oxide (CeO 2 ). may Whether the diffraction peak corresponding to the (220) plane of the oxygen carrier shifts to the high-angle side or the low-angle side, or the amount of shift depends, for example, on the conditions for producing the reducing agent (in particular, pulverization time and , firing temperature and firing time).
The shift amount of the peak position of the diffraction peak corresponding to the (220) plane of the oxygen carrier with respect to the peak position of the diffraction peak corresponding to the (220) plane of cerium oxide (CeO 2 ) is 0.1° or more in 2θ and 0.1° or more. It is preferably less than 6°. The lower limit of the shift amount of the peak position is 0.15° or more, 0.2° or more, 0.25° or more, 0.3° or more, 0.35° or more, 0.4° or more in 2θ. good too. On the other hand, the upper limit of the shift amount of the peak position may be 0.55° or less in 2θ. The lower limit value and the upper limit value can be arbitrarily combined to define a preferable range of the shift amount of the peak position. By setting the shift amount of the peak position within the above range, it can be considered that transition elements other than Ce are more sufficiently and reliably dissolved in the cerium oxide crystal.
If the shift amount of the peak position becomes too large, the fluorite structure, which is the crystal structure of cerium oxide, may not be maintained.
酸素キャリアの（２２０）面に対応する特定の回折ピークは、Ｘ線回折プロファイルにおいて、２θが４４°以上５２°以下の範囲に存在することが好ましく、２θが４６°以上５０°以下の範囲に存在することがより好ましく、２θが４７°以上４９°以下の範囲に存在することがさらに好ましく、４７．６°以上４８以下の範囲に存在することが特に好ましい。この特定の回折ピークが、遷移元素が固溶した酸化セリウムの結晶の（２２０）面に対応する回折ピークに相当する。
酸素キャリアの（２２０）面に対応する回折ピーク（特に、特定の回折ピーク）は、その半値全幅が０．３以上であることが好ましく、０．３５以上であることがより好ましく、０．４以上であることがさらに好ましい。なお、半値全幅は、０．７以下であることが好ましく、０．６５以下であることがより好ましい。これは、酸素キャリアの結晶子サイズの増大が抑制されていること、換言すれば、酸素キャリアの結晶子サイズが比較的小さく維持されていることを意味している。結晶子サイズが比較的小さい酸素キャリアでは、酸素元素の移動距離が短くなるため、還元ガスによる還元剤の還元反応（酸素欠損の誘発反応）および還元剤による二酸化炭素の還元反応のいずれも促進させることができる。 A specific diffraction peak corresponding to the (220) plane of the oxygen carrier preferably exists in the range of 2θ from 44° to 52° in the X-ray diffraction profile, and in the range of 2θ from 46° to 50°. It is more preferable to exist, more preferable to exist in the range of 47° or more and 49° or less, and particularly preferable to exist in the range of 47.6° or more to 48° or less. This specific diffraction peak corresponds to the diffraction peak corresponding to the (220) plane of the cerium oxide crystal in which the transition element is dissolved.
A diffraction peak corresponding to the (220) plane of the oxygen carrier (especially a specific diffraction peak) has a full width at half maximum of preferably 0.3 or more, more preferably 0.35 or more, and 0.4 It is more preferable that it is above. The full width at half maximum is preferably 0.7 or less, more preferably 0.65 or less. This means that the increase in crystallite size of the oxygen carrier is suppressed, in other words, the crystallite size of the oxygen carrier is kept relatively small. An oxygen carrier with a relatively small crystallite size shortens the migration distance of the oxygen element, so both the reduction reaction of the reducing agent by the reducing gas (inducing reaction of oxygen deficiency) and the reduction reaction of carbon dioxide by the reducing agent are promoted. be able to.
酸素キャリアの（２２０）面に対応する回折ピーク（特に、特定の回折ピーク）は、その半値全幅が０．３以上であることが好ましく、０．３５以上であることがより好ましく、０．４以上であることがさらに好ましい。なお、半値全幅は、０．７以下であることが好ましく、０．６５以下であることがより好ましい。これは、酸素キャリアの結晶子サイズの増大が抑制されていること、換言すれば、酸素キャリアの結晶子サイズが比較的小さく維持されていることを意味している。結晶子サイズが比較的小さい酸素キャリアでは、酸素元素の移動距離が短くなるため、還元ガスによる還元剤の還元反応（酸素欠損の誘発反応）および還元剤による二酸化炭素の還元反応のいずれも促進させることができる。 A specific diffraction peak corresponding to the (220) plane of the oxygen carrier preferably exists in the range of 2θ from 44° to 52° in the X-ray diffraction profile, and in the range of 2θ from 46° to 50°. It is more preferable to exist, more preferable to exist in the range of 47° or more and 49° or less, and particularly preferable to exist in the range of 47.6° or more to 48° or less. This specific diffraction peak corresponds to the diffraction peak corresponding to the (220) plane of the cerium oxide crystal in which the transition element is dissolved.
A diffraction peak corresponding to the (220) plane of the oxygen carrier (especially a specific diffraction peak) has a full width at half maximum of preferably 0.3 or more, more preferably 0.35 or more, and 0.4 It is more preferable that it is above. The full width at half maximum is preferably 0.7 or less, more preferably 0.65 or less. This means that the increase in crystallite size of the oxygen carrier is suppressed, in other words, the crystallite size of the oxygen carrier is kept relatively small. An oxygen carrier with a relatively small crystallite size shortens the migration distance of the oxygen element, so both the reduction reaction of the reducing agent by the reducing gas (inducing reaction of oxygen deficiency) and the reduction reaction of carbon dioxide by the reducing agent are promoted. be able to.
酸素キャリアの結晶子サイズの具体的な値は、３２０Å以下であることが好ましく、３００Å以下であることがより好ましく、２８０Å以下であることがさらに好ましく、２７０Å以下であることが特に好ましく、２６０Å以下であることが最も好ましい。このように結晶子サイズが小さい酸素キャリアであれば、酸素元素の移動距離がより短くなるため好ましい。なお、結晶子サイズの下限値は、特に限定されないが、２１０Å以上であることが好ましく、２２０Å以上であることがより好ましく、２３０Å以上であることがさらに好ましく、２５０Å以上であることが特に好ましい。上記下限値を下回る結晶子サイズを有する酸素キャリアを含有する還元剤は、製造が難しくなり易い。なお、下限値と上限値とは、任意に組み合わせて、酸素キャリアの結晶子サイズの好ましい範囲を規定することができる。
本発明者らの検討によれば、上記半値全幅および結晶子サイズの絶対値もさることながら、酸素キャリアの（２２０）面に対応する回折ピーク（特に、特定の回折ピーク）において、その半値全幅に対するピーク強度の比（ピーク強度／半値全幅）と上述した還元剤の反応性との間に、高い相関性があることが判明した。このピーク強度／半値全幅の具体的な値は、６．２以下であることが好ましく、６以下であることがより好ましく、５．５以下または５以下であることがさらに好ましく、４．５以下であることが特に好ましく、４以下であることが最も好ましい。ピーク強度／半値全幅の下限値は、２．５以上であることが好ましく、３以上であることがより好ましい。ピーク強度／半値全幅の値が上記下限値未満であると、酸素キャリアの結晶性が低くなり過ぎ、酸素元素の移動が生じ難くなるおそれがある。
ここで、特定の回折ピークとは、Ｘ線回折プロファイルにおいて、２θで４５°以上４９°以下の範囲で観察される最大強度を有するピークである。このピークに対して、半値全幅に対するピーク強度の比（ピーク強度／半値全幅）が規定される。 The specific value of the crystallite size of the oxygen carrier is preferably 320 Å or less, more preferably 300 Å or less, even more preferably 280 Å or less, particularly preferably 270 Å or less, and 260 Å or less. is most preferred. Such an oxygen carrier having a small crystallite size is preferable because the oxygen element travels a shorter distance. Although the lower limit of the crystallite size is not particularly limited, it is preferably 210 Å or more, more preferably 220 Å or more, further preferably 230 Å or more, and particularly preferably 250 Å or more. A reducing agent containing an oxygen carrier having a crystallite size below the above lower limit tends to be difficult to produce. The lower limit and upper limit can be arbitrarily combined to define a preferred range of crystallite size of the oxygen carrier.
According to the studies of the present inventors, the full width at half maximum and the absolute value of the crystallite size, as well as the diffraction peak corresponding to the (220) plane of the oxygen carrier (in particular, a specific diffraction peak), have a full width at half maximum It was found that there is a high correlation between the ratio of peak intensity to (peak intensity/full width at half maximum) and the reactivity of the reducing agent described above. The specific value of this peak intensity/full width at half maximum is preferably 6.2 or less, more preferably 6 or less, more preferably 5.5 or less or 5 or less, and 4.5 or less. is particularly preferred, and 4 or less is most preferred. The lower limit of peak intensity/full width at half maximum is preferably 2.5 or more, more preferably 3 or more. When the value of peak intensity/full width at half maximum is less than the above lower limit, the crystallinity of the oxygen carrier may become too low, making it difficult for the oxygen element to move.
Here, the specific diffraction peak is the peak having the maximum intensity observed in the range of 45° or more and 49° or less in 2θ in the X-ray diffraction profile. A ratio of peak intensity to full width at half maximum (peak intensity/full width at half maximum) is defined for this peak.
本発明者らの検討によれば、上記半値全幅および結晶子サイズの絶対値もさることながら、酸素キャリアの（２２０）面に対応する回折ピーク（特に、特定の回折ピーク）において、その半値全幅に対するピーク強度の比（ピーク強度／半値全幅）と上述した還元剤の反応性との間に、高い相関性があることが判明した。このピーク強度／半値全幅の具体的な値は、６．２以下であることが好ましく、６以下であることがより好ましく、５．５以下または５以下であることがさらに好ましく、４．５以下であることが特に好ましく、４以下であることが最も好ましい。ピーク強度／半値全幅の下限値は、２．５以上であることが好ましく、３以上であることがより好ましい。ピーク強度／半値全幅の値が上記下限値未満であると、酸素キャリアの結晶性が低くなり過ぎ、酸素元素の移動が生じ難くなるおそれがある。
ここで、特定の回折ピークとは、Ｘ線回折プロファイルにおいて、２θで４５°以上４９°以下の範囲で観察される最大強度を有するピークである。このピークに対して、半値全幅に対するピーク強度の比（ピーク強度／半値全幅）が規定される。 The specific value of the crystallite size of the oxygen carrier is preferably 320 Å or less, more preferably 300 Å or less, even more preferably 280 Å or less, particularly preferably 270 Å or less, and 260 Å or less. is most preferred. Such an oxygen carrier having a small crystallite size is preferable because the oxygen element travels a shorter distance. Although the lower limit of the crystallite size is not particularly limited, it is preferably 210 Å or more, more preferably 220 Å or more, further preferably 230 Å or more, and particularly preferably 250 Å or more. A reducing agent containing an oxygen carrier having a crystallite size below the above lower limit tends to be difficult to produce. The lower limit and upper limit can be arbitrarily combined to define a preferred range of crystallite size of the oxygen carrier.
According to the studies of the present inventors, the full width at half maximum and the absolute value of the crystallite size, as well as the diffraction peak corresponding to the (220) plane of the oxygen carrier (in particular, a specific diffraction peak), have a full width at half maximum It was found that there is a high correlation between the ratio of peak intensity to (peak intensity/full width at half maximum) and the reactivity of the reducing agent described above. The specific value of this peak intensity/full width at half maximum is preferably 6.2 or less, more preferably 6 or less, more preferably 5.5 or less or 5 or less, and 4.5 or less. is particularly preferred, and 4 or less is most preferred. The lower limit of peak intensity/full width at half maximum is preferably 2.5 or more, more preferably 3 or more. When the value of peak intensity/full width at half maximum is less than the above lower limit, the crystallinity of the oxygen carrier may become too low, making it difficult for the oxygen element to move.
Here, the specific diffraction peak is the peak having the maximum intensity observed in the range of 45° or more and 49° or less in 2θ in the X-ray diffraction profile. A ratio of peak intensity to full width at half maximum (peak intensity/full width at half maximum) is defined for this peak.
酸素キャリアはＣｅ以外の遷移元素を含む。酸素キャリアが追加の遷移元素を含むことにより、その結晶構造を適度に歪ませることができる。その結果、酸素キャリアに対する酸素元素の出入りがより円滑になされるようになる。
なお、酸素キャリア（金属酸化物）に含まれる金属元素の合計のモル量に対するセリウムのモル量の比（モル比）は、特に限定されないが、０．６以上であることが好ましく、０．６５以上であることがより好ましく、０．７以上であることがさらに好ましい。なお、モル比の上限は、通常、０．９８以下である。 Oxygen carriers include transition elements other than Ce. Including an additional transition element in the oxygen carrier can moderately strain its crystal structure. As a result, the oxygen element moves in and out of the oxygen carrier more smoothly.
The ratio (molar ratio) of the molar amount of cerium to the total molar amount of the metal elements contained in the oxygen carrier (metal oxide) is not particularly limited, but is preferably 0.6 or more, and preferably 0.65. It is more preferably 0.7 or more, and more preferably 0.7 or more. In addition, the upper limit of the molar ratio is usually 0.98 or less.
なお、酸素キャリア（金属酸化物）に含まれる金属元素の合計のモル量に対するセリウムのモル量の比（モル比）は、特に限定されないが、０．６以上であることが好ましく、０．６５以上であることがより好ましく、０．７以上であることがさらに好ましい。なお、モル比の上限は、通常、０．９８以下である。 Oxygen carriers include transition elements other than Ce. Including an additional transition element in the oxygen carrier can moderately strain its crystal structure. As a result, the oxygen element moves in and out of the oxygen carrier more smoothly.
The ratio (molar ratio) of the molar amount of cerium to the total molar amount of the metal elements contained in the oxygen carrier (metal oxide) is not particularly limited, but is preferably 0.6 or more, and preferably 0.65. It is more preferably 0.7 or more, and more preferably 0.7 or more. In addition, the upper limit of the molar ratio is usually 0.98 or less.
遷移元素は、周期表の第４周期および第５周期に属する元素のうちの少なくとも１種であることが好ましい。かかる元素は、そのイオン半径がＣｅのイオン半径と比較的近くなるため、酸素キャリアの結晶がイオン半径の差により不安定になるのを防止または抑制することができる。
遷移元素の具体例としては、スカンジウム（Ｓｃ）、バナジウム（Ｖ）、クロム（Ｃｒ）、鉄（Ｆｅ）、マンガン（Ｍｎ）、ニッケル（Ｎｉ）、コバルト（Ｃｏ）、銅（Ｃｕ）、亜鉛（Ｚｎ）、ジルコニウム（Ｚｒ）、ニオブ（Ｎｂ）、モリブデン（Ｍｏ）、ルテニウム（Ｒｕ）、ロジウム（Ｒｈ）、パラジウム（Ｐｄ）、ハフニウム（Ｈｆ）、タングステン（Ｗ）、チタン（Ｔｉ）等が挙げられる。これらの遷移元素は、１種または２種以上を組み合わせて使用することができる。中でも、遷移元素としては、Ｆｅ、ＭｎおよびＺｒのうちの１種であることが好ましく、Ｆｅおよび／またはＺｒであることがより好ましい。これらの遷移元素は、そのイオン半径がセリウムのイオン半径より小さいため、酸素キャリアの結晶構造をより適度に歪ませることができ、上記効果をより向上することができる。
なお、酸素キャリアは、上記遷移元素に加えて、遷移元素以外の元素を含有することもできる。 Preferably, the transition element is at least one element belonging to the 4th and 5th periods of the periodic table. Since the ionic radius of such an element is relatively close to that of Ce, it is possible to prevent or suppress the instability of oxygen carrier crystals due to the difference in ionic radius.
Specific examples of transition elements include scandium (Sc), vanadium (V), chromium (Cr), iron (Fe), manganese (Mn), nickel (Ni), cobalt (Co), copper (Cu), zinc ( Zn), zirconium (Zr), niobium (Nb), molybdenum (Mo), ruthenium (Ru), rhodium (Rh), palladium (Pd), hafnium (Hf), tungsten (W), titanium (Ti), etc. be done. These transition elements can be used singly or in combination of two or more. Among them, the transition element is preferably one of Fe, Mn and Zr, more preferably Fe and/or Zr. Since these transition elements have ion radii smaller than that of cerium, they can moderately distort the crystal structure of the oxygen carrier and further improve the above effects.
In addition to the above transition elements, the oxygen carrier can also contain elements other than the transition elements.
遷移元素の具体例としては、スカンジウム（Ｓｃ）、バナジウム（Ｖ）、クロム（Ｃｒ）、鉄（Ｆｅ）、マンガン（Ｍｎ）、ニッケル（Ｎｉ）、コバルト（Ｃｏ）、銅（Ｃｕ）、亜鉛（Ｚｎ）、ジルコニウム（Ｚｒ）、ニオブ（Ｎｂ）、モリブデン（Ｍｏ）、ルテニウム（Ｒｕ）、ロジウム（Ｒｈ）、パラジウム（Ｐｄ）、ハフニウム（Ｈｆ）、タングステン（Ｗ）、チタン（Ｔｉ）等が挙げられる。これらの遷移元素は、１種または２種以上を組み合わせて使用することができる。中でも、遷移元素としては、Ｆｅ、ＭｎおよびＺｒのうちの１種であることが好ましく、Ｆｅおよび／またはＺｒであることがより好ましい。これらの遷移元素は、そのイオン半径がセリウムのイオン半径より小さいため、酸素キャリアの結晶構造をより適度に歪ませることができ、上記効果をより向上することができる。
なお、酸素キャリアは、上記遷移元素に加えて、遷移元素以外の元素を含有することもできる。 Preferably, the transition element is at least one element belonging to the 4th and 5th periods of the periodic table. Since the ionic radius of such an element is relatively close to that of Ce, it is possible to prevent or suppress the instability of oxygen carrier crystals due to the difference in ionic radius.
Specific examples of transition elements include scandium (Sc), vanadium (V), chromium (Cr), iron (Fe), manganese (Mn), nickel (Ni), cobalt (Co), copper (Cu), zinc ( Zn), zirconium (Zr), niobium (Nb), molybdenum (Mo), ruthenium (Ru), rhodium (Rh), palladium (Pd), hafnium (Hf), tungsten (W), titanium (Ti), etc. be done. These transition elements can be used singly or in combination of two or more. Among them, the transition element is preferably one of Fe, Mn and Zr, more preferably Fe and/or Zr. Since these transition elements have ion radii smaller than that of cerium, they can moderately distort the crystal structure of the oxygen carrier and further improve the above effects.
In addition to the above transition elements, the oxygen carrier can also contain elements other than the transition elements.
本発明の還元剤は、酸素キャリア単独で構成されてもよいが、酸素キャリアと酸素キャリアを結合する結合剤と含有して構成されてもよい。後者の態様としては、酸素キャリアの微粒子を結合剤（担体）で結合した態様が挙げられる。この場合、還元剤の形状保持性をより高めることができるとともに、還元剤の比表面積も調整し易くなる。
還元剤が結合剤を含有する場合、結合剤の割合は、還元剤１００質量部に対して６０質量部以下であることが好ましく、５０質量部以下であることがより好ましく、４０質量部以下であることがさらに好ましい。また、結合剤の割合は、還元剤１００質量部に対して１質量部以上、２質量部以上、３質量部以上、４質量部以上、５質量部以上、６質量部以上、７質量部以上、８質量部以上、９質量部以上、１０質量部以上であってもよい。なお、下限値と上限値とは、任意に組み合わせて、結合剤の割合の範囲を規定することができる。還元剤に含まれる結合剤の量を上記範囲とすることにより、還元剤の高い形状保持性を維持しつつ、還元剤による二酸化炭素の一酸化炭素への変換効率をより向上することができる。 The reducing agent of the present invention may be composed of an oxygen carrier alone, or may be composed of an oxygen carrier and a binder that binds the oxygen carrier together. The latter embodiment includes an embodiment in which oxygen carrier fine particles are bound with a binder (carrier). In this case, the shape retention of the reducing agent can be further enhanced, and the specific surface area of the reducing agent can be easily adjusted.
When the reducing agent contains a binder, the ratio of the binder to 100 parts by mass of the reducing agent is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, and 40 parts by mass or less. It is even more preferable to have The ratio of the binder is 1 part by mass or more, 2 parts by mass or more, 3 parts by mass or more, 4 parts by mass or more, 5 parts by mass or more, 6 parts by mass or more, or 7 parts by mass or more with respect to 100 parts by mass of the reducing agent. , 8 parts by mass or more, 9 parts by mass or more, or 10 parts by mass or more. In addition, the lower limit and the upper limit can be combined arbitrarily to define the range of the ratio of the binder. By setting the amount of the binder contained in the reducing agent within the above range, it is possible to further improve the conversion efficiency of carbon dioxide to carbon monoxide by the reducing agent while maintaining high shape retention of the reducing agent.
還元剤が結合剤を含有する場合、結合剤の割合は、還元剤１００質量部に対して６０質量部以下であることが好ましく、５０質量部以下であることがより好ましく、４０質量部以下であることがさらに好ましい。また、結合剤の割合は、還元剤１００質量部に対して１質量部以上、２質量部以上、３質量部以上、４質量部以上、５質量部以上、６質量部以上、７質量部以上、８質量部以上、９質量部以上、１０質量部以上であってもよい。なお、下限値と上限値とは、任意に組み合わせて、結合剤の割合の範囲を規定することができる。還元剤に含まれる結合剤の量を上記範囲とすることにより、還元剤の高い形状保持性を維持しつつ、還元剤による二酸化炭素の一酸化炭素への変換効率をより向上することができる。 The reducing agent of the present invention may be composed of an oxygen carrier alone, or may be composed of an oxygen carrier and a binder that binds the oxygen carrier together. The latter embodiment includes an embodiment in which oxygen carrier fine particles are bound with a binder (carrier). In this case, the shape retention of the reducing agent can be further enhanced, and the specific surface area of the reducing agent can be easily adjusted.
When the reducing agent contains a binder, the ratio of the binder to 100 parts by mass of the reducing agent is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, and 40 parts by mass or less. It is even more preferable to have The ratio of the binder is 1 part by mass or more, 2 parts by mass or more, 3 parts by mass or more, 4 parts by mass or more, 5 parts by mass or more, 6 parts by mass or more, or 7 parts by mass or more with respect to 100 parts by mass of the reducing agent. , 8 parts by mass or more, 9 parts by mass or more, or 10 parts by mass or more. In addition, the lower limit and the upper limit can be combined arbitrarily to define the range of the ratio of the binder. By setting the amount of the binder contained in the reducing agent within the above range, it is possible to further improve the conversion efficiency of carbon dioxide to carbon monoxide by the reducing agent while maintaining high shape retention of the reducing agent.
結合剤としては、原料ガスとの接触や反応条件等に応じて変性し難い化合物であればよく、特に限定されないが、例えば、酸化物、窒化物、酸窒化物、炭化物のような無機材料、炭素材料（グラファイト、グラフェン等）等が挙げられる。
中でも、結合剤としては、酸化物であることが好ましく、マグネシウム（Ｍｇ）、チタン（Ｔｉ）、ジルコニウム（Ｚｒ）、アルミニウム（Ａｌ）およびケイ素（Ｓｉ）のうちの少なくとも１種を含む酸化物であることがより好ましく、酸化アルミニウムであることがさらに好ましい。これらの酸化物は、熱に対する安定性が高く、かつ酸素キャリアの微粒子を安定的に結合し易いことから好ましい。 The binder is not particularly limited as long as it is a compound that is difficult to denature depending on contact with the raw material gas, reaction conditions, etc., but for example, inorganic materials such as oxides, nitrides, oxynitrides, and carbides, Examples include carbon materials (graphite, graphene, etc.).
Among them, the binder is preferably an oxide, and an oxide containing at least one of magnesium (Mg), titanium (Ti), zirconium (Zr), aluminum (Al) and silicon (Si). more preferably aluminum oxide. These oxides are preferable because they are highly stable against heat and tend to stably bind oxygen carrier fine particles.
中でも、結合剤としては、酸化物であることが好ましく、マグネシウム（Ｍｇ）、チタン（Ｔｉ）、ジルコニウム（Ｚｒ）、アルミニウム（Ａｌ）およびケイ素（Ｓｉ）のうちの少なくとも１種を含む酸化物であることがより好ましく、酸化アルミニウムであることがさらに好ましい。これらの酸化物は、熱に対する安定性が高く、かつ酸素キャリアの微粒子を安定的に結合し易いことから好ましい。 The binder is not particularly limited as long as it is a compound that is difficult to denature depending on contact with the raw material gas, reaction conditions, etc., but for example, inorganic materials such as oxides, nitrides, oxynitrides, and carbides, Examples include carbon materials (graphite, graphene, etc.).
Among them, the binder is preferably an oxide, and an oxide containing at least one of magnesium (Mg), titanium (Ti), zirconium (Zr), aluminum (Al) and silicon (Si). more preferably aluminum oxide. These oxides are preferable because they are highly stable against heat and tend to stably bind oxygen carrier fine particles.
還元剤の充填密度は、４ｇ／ｍＬ以下であることが好ましく、０．５ｇ／ｍＬ以上３ｇ／ｍＬ以下であることがより好ましく、１ｇ／ｍＬ以上２．５ｇ／ｍＬ以下であることがさらに好ましい。この充填密度が低過ぎると、ガスの通過速度が速くなり過ぎ、還元剤と原料ガスおよび還元ガスとが接触する時間が減少する。その結果、還元剤による二酸化炭素の一酸化炭素への変換効率や、還元ガスによる酸化状態の還元剤の再生効率が低下し易い。一方、この充填密度が高過ぎると、ガスの通過速度が遅くなり過ぎ、反応が進行し難くなったり、生成ガスを製造するのに長時間を要するようになったりする。
The packing density of the reducing agent is preferably 4 g/mL or less, more preferably 0.5 g/mL or more and 3 g/mL or less, and even more preferably 1 g/mL or more and 2.5 g/mL or less. . If the packing density is too low, the gas passing speed becomes too fast, and the contact time between the reducing agent and the raw material gas and the reducing gas is shortened. As a result, the efficiency of conversion of carbon dioxide to carbon monoxide by the reducing agent and the efficiency of regeneration of the reducing agent in the oxidized state by the reducing gas tend to decrease. On the other hand, if the packing density is too high, the passage speed of the gas becomes too slow, making it difficult for the reaction to proceed or requiring a long time to produce the product gas.
還元剤の細孔容積は、０．１ｃｍ３／ｇ以上であることが好ましく、１ｃｍ３／ｇ以上３０ｃｍ３／ｇ以下であることがより好ましく、５ｃｍ３／ｇ以上２０ｃｍ３／ｇ以下であることがさらに好ましい。この細孔容積が小さ過ぎると、原料ガスおよび還元ガスが還元剤の内部にまで入り難くなる。その結果、還元剤と原料ガスおよび還元ガスとの接触面積が減少し、還元剤による二酸化炭素の一酸化炭素への変換効率や、還元ガスによる酸化状態の還元剤の再生効率が低下し易い。一方、この細孔容積の上限値を超えて大きくしても、それ以上の効果の増大が期待できず、還元剤の種類によっては機械的強度が低下する傾向を示す。
The pore volume of the reducing agent is preferably 0.1 cm 3 /g or more, more preferably 1 cm 3 /g or more and 30 cm 3 /g or less, and 5 cm 3 /g or more and 20 cm 3 /g or less. is more preferred. If the pore volume is too small, it becomes difficult for the raw material gas and the reducing gas to enter the inside of the reducing agent. As a result, the contact area between the reducing agent and the raw material gas and the reducing gas is reduced, and the efficiency of conversion of carbon dioxide to carbon monoxide by the reducing agent and the efficiency of regeneration of the reducing agent in the oxidized state by the reducing gas tend to decrease. On the other hand, even if the pore volume exceeds the upper limit, no further increase in the effect can be expected, and the mechanical strength tends to decrease depending on the type of reducing agent.
還元剤の形状としては、特に限定されないが、例えば、粒状が好ましい。粒状であれば、還元剤の充填密度を上記範囲に調整し易い。
ここで、粒状とは、粉末状、粒子状、塊状、ペレット状等を含む概念であり、その形態も球状、板状、多角状、破砕状、柱状、針状、鱗片状等のいずれでもよい。
還元剤の平均粒径は、１μｍ以上５ｍｍ以下であることが好ましく、１０μｍ以上１ｍｍ以下であることがより好ましく、２０μｍ以上０．５ｍｍ以下であることがさらに好ましい。かかる平均粒径を有する還元剤であれば、その充填密度を上記範囲に調整し易い。 Although the shape of the reducing agent is not particularly limited, it is preferably granular, for example. If it is granular, it is easy to adjust the filling density of the reducing agent to the above range.
Here, "granular" is a concept including powdery, particulate, lumpy, pellet-like, etc., and its shape may be any of spherical, plate-like, polygonal, crushed, columnar, needle-like, scale-like, etc. .
The average particle size of the reducing agent is preferably 1 μm or more and 5 mm or less, more preferably 10 μm or more and 1 mm or less, and even more preferably 20 μm or more and 0.5 mm or less. With a reducing agent having such an average particle size, it is easy to adjust the packing density within the above range.
ここで、粒状とは、粉末状、粒子状、塊状、ペレット状等を含む概念であり、その形態も球状、板状、多角状、破砕状、柱状、針状、鱗片状等のいずれでもよい。
還元剤の平均粒径は、１μｍ以上５ｍｍ以下であることが好ましく、１０μｍ以上１ｍｍ以下であることがより好ましく、２０μｍ以上０．５ｍｍ以下であることがさらに好ましい。かかる平均粒径を有する還元剤であれば、その充填密度を上記範囲に調整し易い。 Although the shape of the reducing agent is not particularly limited, it is preferably granular, for example. If it is granular, it is easy to adjust the filling density of the reducing agent to the above range.
Here, "granular" is a concept including powdery, particulate, lumpy, pellet-like, etc., and its shape may be any of spherical, plate-like, polygonal, crushed, columnar, needle-like, scale-like, etc. .
The average particle size of the reducing agent is preferably 1 μm or more and 5 mm or less, more preferably 10 μm or more and 1 mm or less, and even more preferably 20 μm or more and 0.5 mm or less. With a reducing agent having such an average particle size, it is easy to adjust the packing density within the above range.
なお、本明細書において、平均粒径とは、電子顕微鏡で観察される一視野中の任意の２００個の還元剤の粒径の平均値を意味する。この際、「粒径」とは、還元剤の輪郭線上の２点間の距離のうち最大の長さを意味する。なお、還元剤が柱状である場合、その端面の輪郭線上の２点間の距離のうち最大の長さを「粒径」とする。また、平均粒径は、例えば、塊状などであり、一次粒子が凝集している場合には、二次粒子の平均粒径を意味する。
還元剤のＢＥＴ比表面積は、１ｍ２／ｇ以上５００ｍ２／ｇ以下であることが好ましく、３ｍ２／ｇ以上４５０ｍ２／ｇ以下であることがより好ましく、５ｍ２／ｇ以上４００ｍ２／ｇ以下であることがさらに好ましい。ＢＥＴ比表面積が上記範囲内であることで、還元剤による二酸化炭素の一酸化炭素への変換効率を向上させ易くなる。 In this specification, the average particle size means the average value of the particle sizes of arbitrary 200 reducing agents in one field observed with an electron microscope. In this case, the "particle size" means the maximum length among the distances between two points on the contour line of the reducing agent. When the reducing agent is columnar, the maximum length of the distance between two points on the contour line of the end face is defined as the "particle diameter". Further, the average particle size is, for example, in the form of lumps, and means the average particle size of the secondary particles when the primary particles are agglomerated.
The BET specific surface area of the reducing agent is preferably 1 m 2 /g or more and 500 m 2 /g or less, more preferably 3 m 2 /g or more and 450 m 2 /g or less, and 5 m 2 /g or more and 400 m 2 /g. More preferably: When the BET specific surface area is within the above range, it becomes easier to improve the conversion efficiency of carbon dioxide to carbon monoxide by the reducing agent.
還元剤のＢＥＴ比表面積は、１ｍ２／ｇ以上５００ｍ２／ｇ以下であることが好ましく、３ｍ２／ｇ以上４５０ｍ２／ｇ以下であることがより好ましく、５ｍ２／ｇ以上４００ｍ２／ｇ以下であることがさらに好ましい。ＢＥＴ比表面積が上記範囲内であることで、還元剤による二酸化炭素の一酸化炭素への変換効率を向上させ易くなる。 In this specification, the average particle size means the average value of the particle sizes of arbitrary 200 reducing agents in one field observed with an electron microscope. In this case, the "particle size" means the maximum length among the distances between two points on the contour line of the reducing agent. When the reducing agent is columnar, the maximum length of the distance between two points on the contour line of the end face is defined as the "particle diameter". Further, the average particle size is, for example, in the form of lumps, and means the average particle size of the secondary particles when the primary particles are agglomerated.
The BET specific surface area of the reducing agent is preferably 1 m 2 /g or more and 500 m 2 /g or less, more preferably 3 m 2 /g or more and 450 m 2 /g or less, and 5 m 2 /g or more and 400 m 2 /g. More preferably: When the BET specific surface area is within the above range, it becomes easier to improve the conversion efficiency of carbon dioxide to carbon monoxide by the reducing agent.
また、本発明では、Ｃｅ以外の遷移元素が酸素キャリア（酸化セリウム）に安定的に固溶されているため、低温（４００℃程度）～高温（８５０℃程度）の広い範囲において、還元剤の酸素容量を高い状態に維持することができる。すなわち、本発明の還元剤は、広い温度範囲で二酸化炭素を一酸化炭素へ効率よく変換することができ、水素を含む還元ガスによって効率的に還元されることができる。
還元剤に含まれる酸素キャリアの４００℃における酸素容量は、０．１～４０質量％であることが好ましく、０．５～３０質量％であることがより好ましい。還元剤に含まれる酸素キャリアの低温における酸素容量が上記範囲であれば、実稼働時の温度（６５０℃を上回る温度）においても酸素容量が十分に高いことを意味しており、二酸化炭素の一酸化炭素への変換効率が極めて高い還元剤であると言える。 In addition, in the present invention, since the transition element other than Ce is stably dissolved in the oxygen carrier (cerium oxide), the reducing agent can be used in a wide range from low temperature (about 400 ° C.) to high temperature (about 850 ° C.). Oxygen capacity can be maintained at a high level. That is, the reducing agent of the present invention can efficiently convert carbon dioxide to carbon monoxide over a wide temperature range, and can be efficiently reduced by a hydrogen-containing reducing gas.
The oxygen capacity at 400° C. of the oxygen carrier contained in the reducing agent is preferably 0.1 to 40% by mass, more preferably 0.5 to 30% by mass. If the oxygen capacity at low temperature of the oxygen carrier contained in the reducing agent is within the above range, it means that the oxygen capacity is sufficiently high even at the temperature during actual operation (temperature above 650 ° C.), and it is one of carbon dioxide. It can be said that it is a reducing agent with extremely high conversion efficiency to carbon oxide.
還元剤に含まれる酸素キャリアの４００℃における酸素容量は、０．１～４０質量％であることが好ましく、０．５～３０質量％であることがより好ましい。還元剤に含まれる酸素キャリアの低温における酸素容量が上記範囲であれば、実稼働時の温度（６５０℃を上回る温度）においても酸素容量が十分に高いことを意味しており、二酸化炭素の一酸化炭素への変換効率が極めて高い還元剤であると言える。 In addition, in the present invention, since the transition element other than Ce is stably dissolved in the oxygen carrier (cerium oxide), the reducing agent can be used in a wide range from low temperature (about 400 ° C.) to high temperature (about 850 ° C.). Oxygen capacity can be maintained at a high level. That is, the reducing agent of the present invention can efficiently convert carbon dioxide to carbon monoxide over a wide temperature range, and can be efficiently reduced by a hydrogen-containing reducing gas.
The oxygen capacity at 400° C. of the oxygen carrier contained in the reducing agent is preferably 0.1 to 40% by mass, more preferably 0.5 to 30% by mass. If the oxygen capacity at low temperature of the oxygen carrier contained in the reducing agent is within the above range, it means that the oxygen capacity is sufficiently high even at the temperature during actual operation (temperature above 650 ° C.), and it is one of carbon dioxide. It can be said that it is a reducing agent with extremely high conversion efficiency to carbon oxide.
［還元剤の製造方法］
次に、還元剤の製造方法について説明する。
還元剤の製造方法としては、特に限定されないが、例えば、ゾル－ゲル法、共沈法、固相法、水熱合成法等が挙げられる。
還元剤は、一例として、例えば、次のようにして製造することができる。まず、還元剤を構成する金属元素の塩（上記無機結合剤を使用する場合、無機結合剤を構成する元素の塩を含んでもよい。）を水に溶解して水溶液を調製する。次いで、この水溶液をゲル化した後、乾燥および焼成する。すなわち、本発明の還元剤は、いわゆるゾル－ゲル法により、容易かつ確実に製造することができる。
なお、水溶液の調整には、例えば、クエン酸、酢酸、リンゴ酸、酒石酸、塩酸、硝酸またはこれらの混合物等で酸性に調整した酸性水を用いてもよい。 [Method for producing reducing agent]
Next, a method for producing the reducing agent will be described.
The method for producing the reducing agent is not particularly limited, and examples thereof include a sol-gel method, a coprecipitation method, a solid phase method, a hydrothermal synthesis method and the like.
For example, the reducing agent can be produced as follows. First, an aqueous solution is prepared by dissolving a salt of a metal element that constitutes a reducing agent (when using the inorganic binder, the salt of the element that constitutes the inorganic binder may be included) in water. Then, after gelling the aqueous solution, it is dried and baked. That is, the reducing agent of the present invention can be easily and reliably produced by the so-called sol-gel method.
To prepare the aqueous solution, for example, acidic water adjusted to be acidic with citric acid, acetic acid, malic acid, tartaric acid, hydrochloric acid, nitric acid, or a mixture thereof may be used.
次に、還元剤の製造方法について説明する。
還元剤の製造方法としては、特に限定されないが、例えば、ゾル－ゲル法、共沈法、固相法、水熱合成法等が挙げられる。
還元剤は、一例として、例えば、次のようにして製造することができる。まず、還元剤を構成する金属元素の塩（上記無機結合剤を使用する場合、無機結合剤を構成する元素の塩を含んでもよい。）を水に溶解して水溶液を調製する。次いで、この水溶液をゲル化した後、乾燥および焼成する。すなわち、本発明の還元剤は、いわゆるゾル－ゲル法により、容易かつ確実に製造することができる。
なお、水溶液の調整には、例えば、クエン酸、酢酸、リンゴ酸、酒石酸、塩酸、硝酸またはこれらの混合物等で酸性に調整した酸性水を用いてもよい。 [Method for producing reducing agent]
Next, a method for producing the reducing agent will be described.
The method for producing the reducing agent is not particularly limited, and examples thereof include a sol-gel method, a coprecipitation method, a solid phase method, a hydrothermal synthesis method and the like.
For example, the reducing agent can be produced as follows. First, an aqueous solution is prepared by dissolving a salt of a metal element that constitutes a reducing agent (when using the inorganic binder, the salt of the element that constitutes the inorganic binder may be included) in water. Then, after gelling the aqueous solution, it is dried and baked. That is, the reducing agent of the present invention can be easily and reliably produced by the so-called sol-gel method.
To prepare the aqueous solution, for example, acidic water adjusted to be acidic with citric acid, acetic acid, malic acid, tartaric acid, hydrochloric acid, nitric acid, or a mixture thereof may be used.
金属元素の塩としては、例えば、硝酸塩、硫酸塩、塩化物、水酸化物、炭酸塩またはこれらの複合物等が挙げられるが、これらの中でも硝酸塩であることが好ましい。また、金属元素の塩には、必要に応じて、水和物を使用してもよい。
ゲルの乾燥は、好ましくは２０℃以上２００℃以下、より好ましくは５０℃以上１５０℃以下の温度で、好ましくは０．５時間以上２０時間以下、より好ましくは１時間以上１５時間以下の時間で行うとよい。このように乾燥することで、ゲルを均一に乾燥させることができる。 Examples of salts of metal elements include nitrates, sulfates, chlorides, hydroxides, carbonates, and composites thereof. Of these, nitrates are preferred. Moreover, you may use a hydrate for the salt of a metal element as needed.
The gel is dried at a temperature of preferably 20° C. to 200° C., more preferably 50° C. to 150° C., preferably 0.5 hours to 20 hours, more preferably 1 hour to 15 hours. do it. By drying in this manner, the gel can be dried uniformly.
ゲルの乾燥は、好ましくは２０℃以上２００℃以下、より好ましくは５０℃以上１５０℃以下の温度で、好ましくは０．５時間以上２０時間以下、より好ましくは１時間以上１５時間以下の時間で行うとよい。このように乾燥することで、ゲルを均一に乾燥させることができる。 Examples of salts of metal elements include nitrates, sulfates, chlorides, hydroxides, carbonates, and composites thereof. Of these, nitrates are preferred. Moreover, you may use a hydrate for the salt of a metal element as needed.
The gel is dried at a temperature of preferably 20° C. to 200° C., more preferably 50° C. to 150° C., preferably 0.5 hours to 20 hours, more preferably 1 hour to 15 hours. do it. By drying in this manner, the gel can be dried uniformly.
ゲルの焼成は、好ましくは３００℃以上１２００℃以下、より好ましくは７００℃以上１０００℃以下での温度で、好ましくは１時間以上２４時間以下、より好ましくは１．５時間以上２０時間以下の時間で行うとよい。ゲルは、焼成により、好ましくは酸化物となるが、上記焼成条件での焼成により還元剤に容易に変換され得る。また、上記焼成条件で焼成すれば、還元剤の過度の粒子成長を防ぐこともできる。
上記焼成温度に到達するまでは、昇温速度１℃／分以上２０℃／分以下、好ましくは昇温速度２℃／分以上１０℃／分以下で昇温するとよい。これにより、還元剤の粒子の成長を促進させるとともに、結晶（粒子）の割れを回避することもできる。 The gel is baked at a temperature of preferably 300° C. or higher and 1200° C. or lower, more preferably 700° C. or higher and 1000° C. or lower, for preferably 1 hour or more and 24 hours or less, more preferably 1.5 hours or more and 20 hours or less. should be done with The gel preferably becomes an oxide upon calcination, but can be easily converted to a reducing agent by calcination under the above calcination conditions. Further, if the firing is performed under the above firing conditions, excessive particle growth of the reducing agent can be prevented.
The temperature should be raised at a rate of 1° C./min to 20° C./min, preferably at a rate of 2° C./min to 10° C./min until the firing temperature is reached. As a result, the growth of the reducing agent particles can be promoted, and cracking of the crystals (particles) can be avoided.
上記焼成温度に到達するまでは、昇温速度１℃／分以上２０℃／分以下、好ましくは昇温速度２℃／分以上１０℃／分以下で昇温するとよい。これにより、還元剤の粒子の成長を促進させるとともに、結晶（粒子）の割れを回避することもできる。 The gel is baked at a temperature of preferably 300° C. or higher and 1200° C. or lower, more preferably 700° C. or higher and 1000° C. or lower, for preferably 1 hour or more and 24 hours or less, more preferably 1.5 hours or more and 20 hours or less. should be done with The gel preferably becomes an oxide upon calcination, but can be easily converted to a reducing agent by calcination under the above calcination conditions. Further, if the firing is performed under the above firing conditions, excessive particle growth of the reducing agent can be prevented.
The temperature should be raised at a rate of 1° C./min to 20° C./min, preferably at a rate of 2° C./min to 10° C./min until the firing temperature is reached. As a result, the growth of the reducing agent particles can be promoted, and cracking of the crystals (particles) can be avoided.
また、還元剤は、次のようにして製造することもできる。
まず、還元剤を構成する金属元素のそれぞれを含む酸化物を混合しつつ粉砕する。粉砕には、例えば、ボールミル、ビーズミル、ジェットミル、ハンマーミル等を使用することができる。また、この粉砕は、乾式または湿式のいずれで行ってもよい。
結合剤を使用する場合、上記酸化物とともに混合される。結合剤には、上記無機結合剤の他、有機結合剤（有機バインダー）を使用することができる。有機物としては、例えば、オレフィン系樹脂、アクリル系樹脂、スチレン系樹脂、エステル系樹脂、エーテル系樹脂、ビニル系樹脂のような各種樹脂や、各種ワックス、各種脂肪酸等が挙げられる。また、この場合、酸化物には、ゾル－ゲル法、共沈法、固相法、水熱合成法等を使用して製造した、上述の酸化物を使用することができる。
次に、粉砕後の塊状物を粉砕した後、焼成する。この焼成は、好ましくは３００℃以上１２００℃以下、より好ましくは７００℃以上１０００℃以下での温度で、好ましくは１時間以上２４時間以下、より好ましくは１．５時間以上２０時間以下の時間で行うとよい。
このとき、有機結合剤の一部または全部は、焼成により消失してもよい。
その後、焼成した塊状物を上記と同様に粉砕することにより、還元剤を得ることができる。 Alternatively, the reducing agent can be produced as follows.
First, oxides containing each of the metal elements constituting the reducing agent are mixed and pulverized. For pulverization, for example, a ball mill, bead mill, jet mill, hammer mill or the like can be used. Also, this pulverization may be carried out either dry or wet.
If a binder is used, it is mixed with the oxide. As the binder, an organic binder (organic binder) can be used in addition to the above inorganic binders. Examples of organic substances include various resins such as olefin resins, acrylic resins, styrene resins, ester resins, ether resins, and vinyl resins, various waxes, and various fatty acids. In this case, the oxides can be the above-described oxides produced using the sol-gel method, coprecipitation method, solid-phase method, hydrothermal synthesis method, or the like.
Next, the pulverized agglomerates are pulverized and then fired. This calcination is preferably performed at a temperature of 300° C. or higher and 1200° C. or lower, more preferably 700° C. or higher and 1000° C. or lower, for preferably 1 hour or more and 24 hours or less, more preferably 1.5 hours or more and 20 hours or less. do it.
At this time, part or all of the organic binder may disappear by firing.
Thereafter, the reducing agent can be obtained by pulverizing the fired lumps in the same manner as described above.
まず、還元剤を構成する金属元素のそれぞれを含む酸化物を混合しつつ粉砕する。粉砕には、例えば、ボールミル、ビーズミル、ジェットミル、ハンマーミル等を使用することができる。また、この粉砕は、乾式または湿式のいずれで行ってもよい。
結合剤を使用する場合、上記酸化物とともに混合される。結合剤には、上記無機結合剤の他、有機結合剤（有機バインダー）を使用することができる。有機物としては、例えば、オレフィン系樹脂、アクリル系樹脂、スチレン系樹脂、エステル系樹脂、エーテル系樹脂、ビニル系樹脂のような各種樹脂や、各種ワックス、各種脂肪酸等が挙げられる。また、この場合、酸化物には、ゾル－ゲル法、共沈法、固相法、水熱合成法等を使用して製造した、上述の酸化物を使用することができる。
次に、粉砕後の塊状物を粉砕した後、焼成する。この焼成は、好ましくは３００℃以上１２００℃以下、より好ましくは７００℃以上１０００℃以下での温度で、好ましくは１時間以上２４時間以下、より好ましくは１．５時間以上２０時間以下の時間で行うとよい。
このとき、有機結合剤の一部または全部は、焼成により消失してもよい。
その後、焼成した塊状物を上記と同様に粉砕することにより、還元剤を得ることができる。 Alternatively, the reducing agent can be produced as follows.
First, oxides containing each of the metal elements constituting the reducing agent are mixed and pulverized. For pulverization, for example, a ball mill, bead mill, jet mill, hammer mill or the like can be used. Also, this pulverization may be carried out either dry or wet.
If a binder is used, it is mixed with the oxide. As the binder, an organic binder (organic binder) can be used in addition to the above inorganic binders. Examples of organic substances include various resins such as olefin resins, acrylic resins, styrene resins, ester resins, ether resins, and vinyl resins, various waxes, and various fatty acids. In this case, the oxides can be the above-described oxides produced using the sol-gel method, coprecipitation method, solid-phase method, hydrothermal synthesis method, or the like.
Next, the pulverized agglomerates are pulverized and then fired. This calcination is preferably performed at a temperature of 300° C. or higher and 1200° C. or lower, more preferably 700° C. or higher and 1000° C. or lower, for preferably 1 hour or more and 24 hours or less, more preferably 1.5 hours or more and 20 hours or less. do it.
At this time, part or all of the organic binder may disappear by firing.
Thereafter, the reducing agent can be obtained by pulverizing the fired lumps in the same manner as described above.
［還元剤の使用方法］
本発明の還元剤は、上述したように、例えば、ケミカルルーピング法で利用することができる。また、本発明の還元剤は、上述したように、接触により二酸化炭素を還元して一酸化炭素（炭素有価物）を生成する用途に使用することができる。
より具体的には、二酸化炭素の還元反応と、還元剤の還元反応とを行うとよく、還元剤は、二酸化炭素の還元反応と還元剤の還元反応との間で循環するように使用することが好ましい。なお、還元剤の還元反応では、他の還元物質を含む還元ガスを使用する。 [How to use the reducing agent]
The reducing agent of the present invention can be used, for example, in the chemical looping method, as described above. Moreover, as described above, the reducing agent of the present invention can be used for the application of reducing carbon dioxide by contact to produce carbon monoxide (carbon valuables).
More specifically, a reduction reaction of carbon dioxide and a reduction reaction of a reducing agent are preferably performed, and the reducing agent is used so as to circulate between the reduction reaction of carbon dioxide and the reduction reaction of the reducing agent. is preferred. In addition, in the reduction reaction of the reducing agent, a reducing gas containing other reducing substances is used.
本発明の還元剤は、上述したように、例えば、ケミカルルーピング法で利用することができる。また、本発明の還元剤は、上述したように、接触により二酸化炭素を還元して一酸化炭素（炭素有価物）を生成する用途に使用することができる。
より具体的には、二酸化炭素の還元反応と、還元剤の還元反応とを行うとよく、還元剤は、二酸化炭素の還元反応と還元剤の還元反応との間で循環するように使用することが好ましい。なお、還元剤の還元反応では、他の還元物質を含む還元ガスを使用する。 [How to use the reducing agent]
The reducing agent of the present invention can be used, for example, in the chemical looping method, as described above. Moreover, as described above, the reducing agent of the present invention can be used for the application of reducing carbon dioxide by contact to produce carbon monoxide (carbon valuables).
More specifically, a reduction reaction of carbon dioxide and a reduction reaction of a reducing agent are preferably performed, and the reducing agent is used so as to circulate between the reduction reaction of carbon dioxide and the reduction reaction of the reducing agent. is preferred. In addition, in the reduction reaction of the reducing agent, a reducing gas containing other reducing substances is used.
また、本発明の還元剤は、いわゆる逆水性ガスシフト反応に使用することが好ましい。逆水性ガスシフト反応とは、二酸化炭素と水素とから、一酸化炭素と水とを生成する反応である。逆水性ガスシフト反応は、ケミカルルーピング法を適用する場合、還元剤の還元反応（第１プロセス）と二酸化炭素の還元反応（第２プロセス）とに分割して行われ、還元剤の還元反応が下記式（Ａ）で示す反応となり、二酸化炭素の還元反応が下記式（Ｂ）で示す反応となる。
In addition, the reducing agent of the present invention is preferably used for so-called reverse water gas shift reaction. The reverse water gas shift reaction is a reaction that produces carbon monoxide and water from carbon dioxide and hydrogen. When the chemical looping method is applied, the reverse water gas shift reaction is divided into a reducing agent reduction reaction (first process) and a carbon dioxide reduction reaction (second process). The reaction is represented by the formula (A), and the reduction reaction of carbon dioxide is represented by the following formula (B).
Ｈ２（ガス） ＋ ＭＯｘ（固体） → Ｈ２Ｏ（ガス） ＋ ＭＯｘ－１（固体） （Ａ）
ＣＯ２（ガス） ＋ ＭＯｘ－１（固体） → ＣＯ（ガス） ＋ ＭＯｘ（固体） （Ｂ）
なお、式（Ａ）および（Ｂ）において、ｘは、通常２である。
すなわち、還元剤の還元反応では、還元物質の一種である水素が酸化されて水が生成される。また、二酸化炭素の還元反応では、二酸化炭素が還元されて炭素有価物の一種である一酸化炭素が生成される。 H 2 (gas) + MO x (solid) → H 2 O (gas) + MO x−1 (solid) (A)
CO 2 (gas) + MO x−1 (solid) → CO (gas) + MO x (solid) (B)
In formulas (A) and (B), x is usually 2.
That is, in the reduction reaction of the reducing agent, hydrogen, which is one type of reducing substance, is oxidized to produce water. In addition, in the reduction reaction of carbon dioxide, carbon monoxide, which is a type of carbon valuables, is produced by reducing carbon dioxide.
ＣＯ２（ガス） ＋ ＭＯｘ－１（固体） → ＣＯ（ガス） ＋ ＭＯｘ（固体） （Ｂ）
なお、式（Ａ）および（Ｂ）において、ｘは、通常２である。
すなわち、還元剤の還元反応では、還元物質の一種である水素が酸化されて水が生成される。また、二酸化炭素の還元反応では、二酸化炭素が還元されて炭素有価物の一種である一酸化炭素が生成される。 H 2 (gas) + MO x (solid) → H 2 O (gas) + MO x−1 (solid) (A)
CO 2 (gas) + MO x−1 (solid) → CO (gas) + MO x (solid) (B)
In formulas (A) and (B), x is usually 2.
That is, in the reduction reaction of the reducing agent, hydrogen, which is one type of reducing substance, is oxidized to produce water. In addition, in the reduction reaction of carbon dioxide, carbon monoxide, which is a type of carbon valuables, is produced by reducing carbon dioxide.
還元剤の還元反応における反応温度（還元剤の還元ガスとの接触温度）は、還元反応が進行できる温度であればよいが、６５０℃を上回る温度であることが好ましく、７００℃以上であることがより好ましく、７５０℃以上であることがさらに好ましく、８００℃以上であることが特に好ましい。かかる温度範囲で、効率的な還元剤の還元反応を進行させることができる。
この反応温度の上限は、１０５０℃以下であることが好ましく、１０００℃以下であることがより好ましく、９５０℃以下であることがさらに好ましく、９００℃以下であることが特に好ましく、８５０℃以下であることが最も好ましい。反応温度の上限を上記範囲に設定することにより、経済性の向上を図ることができる。
なお、下限値と上限値とは、任意に組み合わせて、反応温度の範囲を規定することができる。 The reaction temperature in the reduction reaction of the reducing agent (the contact temperature of the reducing agent with the reducing gas) may be any temperature at which the reduction reaction can proceed, but is preferably above 650°C, and is preferably 700°C or higher. is more preferred, 750° C. or higher is even more preferred, and 800° C. or higher is particularly preferred. Within this temperature range, the reduction reaction of the reducing agent can proceed efficiently.
The upper limit of the reaction temperature is preferably 1050° C. or lower, more preferably 1000° C. or lower, even more preferably 950° C. or lower, particularly preferably 900° C. or lower, and 850° C. or lower. Most preferably there is. By setting the upper limit of the reaction temperature within the above range, economic efficiency can be improved.
In addition, the lower limit and the upper limit can be arbitrarily combined to define the range of the reaction temperature.
この反応温度の上限は、１０５０℃以下であることが好ましく、１０００℃以下であることがより好ましく、９５０℃以下であることがさらに好ましく、９００℃以下であることが特に好ましく、８５０℃以下であることが最も好ましい。反応温度の上限を上記範囲に設定することにより、経済性の向上を図ることができる。
なお、下限値と上限値とは、任意に組み合わせて、反応温度の範囲を規定することができる。 The reaction temperature in the reduction reaction of the reducing agent (the contact temperature of the reducing agent with the reducing gas) may be any temperature at which the reduction reaction can proceed, but is preferably above 650°C, and is preferably 700°C or higher. is more preferred, 750° C. or higher is even more preferred, and 800° C. or higher is particularly preferred. Within this temperature range, the reduction reaction of the reducing agent can proceed efficiently.
The upper limit of the reaction temperature is preferably 1050° C. or lower, more preferably 1000° C. or lower, even more preferably 950° C. or lower, particularly preferably 900° C. or lower, and 850° C. or lower. Most preferably there is. By setting the upper limit of the reaction temperature within the above range, economic efficiency can be improved.
In addition, the lower limit and the upper limit can be arbitrarily combined to define the range of the reaction temperature.
また、還元剤の還元反応の際、酸化状態の還元剤に接触させる水素（還元ガス）の量は、還元剤１ｇに対して１ｍｍｏｌ以上５０ｍｍｏｌ以下であることが好ましく、２．５ｍｍｏｌ以上３５ｍｍｏｌ以下であることがより好ましく、５ｍｍｏｌ以上２０ｍｍｏｌ以下であることがさらに好ましい。本発明の還元剤は、酸素元素の出入りが円滑になされるため、水素利用率が高い。したがって、本発明の還元剤は、少量の水素で十分に還元（再生）される。よって、水素の生成に必要なエネルギーを減少させること、ひいてはエネルギーを得る際に発生する二酸化炭素の削減にも寄与する。
なお、水素利用率（％）は、還元剤１ｇに接触させた水素投入量（モル数）に対する生成した一酸化炭素の量（モル数）の比率を１００分率で表した値である。 Further, in the reduction reaction of the reducing agent, the amount of hydrogen (reducing gas) brought into contact with the reducing agent in an oxidized state is preferably 1 mmol or more and 50 mmol or less, more preferably 2.5 mmol or more and 35 mmol or less, with respect to 1 g of the reducing agent. more preferably 5 mmol or more and 20 mmol or less. The reducing agent of the present invention has a high hydrogen utilization rate because the oxygen element enters and exits smoothly. Therefore, the reducing agent of the present invention is sufficiently reduced (regenerated) with a small amount of hydrogen. Therefore, it contributes to the reduction of the energy required for hydrogen production, and thus the reduction of carbon dioxide generated when the energy is obtained.
The hydrogen utilization rate (%) is the ratio of the amount (number of moles) of generated carbon monoxide to the amount (number of moles) of hydrogen brought into contact with 1 g of the reducing agent, expressed as a percentage.
なお、水素利用率（％）は、還元剤１ｇに接触させた水素投入量（モル数）に対する生成した一酸化炭素の量（モル数）の比率を１００分率で表した値である。 Further, in the reduction reaction of the reducing agent, the amount of hydrogen (reducing gas) brought into contact with the reducing agent in an oxidized state is preferably 1 mmol or more and 50 mmol or less, more preferably 2.5 mmol or more and 35 mmol or less, with respect to 1 g of the reducing agent. more preferably 5 mmol or more and 20 mmol or less. The reducing agent of the present invention has a high hydrogen utilization rate because the oxygen element enters and exits smoothly. Therefore, the reducing agent of the present invention is sufficiently reduced (regenerated) with a small amount of hydrogen. Therefore, it contributes to the reduction of the energy required for hydrogen production, and thus the reduction of carbon dioxide generated when the energy is obtained.
The hydrogen utilization rate (%) is the ratio of the amount (number of moles) of generated carbon monoxide to the amount (number of moles) of hydrogen brought into contact with 1 g of the reducing agent, expressed as a percentage.
さらに、還元剤の還元反応の際、水素を含む還元ガスと接触させることにより、還元剤には、所定の割合で可逆的な酸素欠損量を生じる。この具体的な割合は、還元剤に含まれる酸素キャリアの質量に対して１．６％以上であることが好ましく、２％以上であることがより好ましく、２．５％以上であることがさらに好ましい。かかる割合で、酸素欠陥を生じさせることにより、二酸化炭素の一酸化炭素への変換をさらに促進させることができる。酸素欠損量の上限は、特に限定されないが、通常、１０％程度である。
なお、酸素欠損量は、後述する実施例に記載の方法により求めることができる。 Furthermore, when the reducing agent is brought into contact with a reducing gas containing hydrogen during the reduction reaction of the reducing agent, a reversible amount of oxygen deficiency is generated in the reducing agent at a predetermined rate. This specific ratio is preferably 1.6% or more, more preferably 2% or more, and further preferably 2.5% or more with respect to the mass of the oxygen carrier contained in the reducing agent. preferable. The conversion of carbon dioxide to carbon monoxide can be further promoted by creating oxygen defects at such a rate. Although the upper limit of the oxygen deficiency amount is not particularly limited, it is usually about 10%.
The amount of oxygen deficiency can be determined by the method described in Examples below.
なお、酸素欠損量は、後述する実施例に記載の方法により求めることができる。 Furthermore, when the reducing agent is brought into contact with a reducing gas containing hydrogen during the reduction reaction of the reducing agent, a reversible amount of oxygen deficiency is generated in the reducing agent at a predetermined rate. This specific ratio is preferably 1.6% or more, more preferably 2% or more, and further preferably 2.5% or more with respect to the mass of the oxygen carrier contained in the reducing agent. preferable. The conversion of carbon dioxide to carbon monoxide can be further promoted by creating oxygen defects at such a rate. Although the upper limit of the oxygen deficiency amount is not particularly limited, it is usually about 10%.
The amount of oxygen deficiency can be determined by the method described in Examples below.
また、二酸化炭素の還元反応における反応温度（還元剤の二酸化炭素との接触温度）は、６５０℃を上回る温度であることが好ましく、７００℃以上であることがより好ましく、７５０℃以上であることがさらに好ましく、８００℃以上であることが特に好ましい。かかる温度範囲で、効率的な二酸化炭素の還元反応を進行させることができる。
この反応温度の上限は、１０５０℃以下であることが好ましく、１０００℃以下であることがより好ましく、９５０℃以下であることがさらに好ましく、９００℃以下であることが特に好ましく、８５０℃以下であることが最も好ましい。還元剤は、低温下でも高い効率で二酸化炭素の一酸化炭素への還元反応を行うことができるので、二酸化炭素の還元反応を比較的低温に設定することができる。また、反応温度の上限を上記範囲に設定することにより、廃熱活用が容易になるばかりでなく、更なる経済性の向上を図ることができる。
なお、下限値と上限値とは、任意に組み合わせて、反応温度の範囲を規定することができる。 In addition, the reaction temperature (the contact temperature of the reducing agent with carbon dioxide) in the reduction reaction of carbon dioxide is preferably a temperature above 650°C, more preferably 700°C or higher, and 750°C or higher. is more preferable, and 800° C. or higher is particularly preferable. An efficient carbon dioxide reduction reaction can proceed within this temperature range.
The upper limit of the reaction temperature is preferably 1050° C. or lower, more preferably 1000° C. or lower, even more preferably 950° C. or lower, particularly preferably 900° C. or lower, and 850° C. or lower. Most preferably there is. Since the reducing agent can reduce carbon dioxide to carbon monoxide with high efficiency even at low temperatures, the reduction reaction of carbon dioxide can be set to a relatively low temperature. Further, by setting the upper limit of the reaction temperature within the above range, it is possible not only to facilitate utilization of waste heat, but also to further improve economic efficiency.
In addition, the lower limit and the upper limit can be arbitrarily combined to define the range of the reaction temperature.
この反応温度の上限は、１０５０℃以下であることが好ましく、１０００℃以下であることがより好ましく、９５０℃以下であることがさらに好ましく、９００℃以下であることが特に好ましく、８５０℃以下であることが最も好ましい。還元剤は、低温下でも高い効率で二酸化炭素の一酸化炭素への還元反応を行うことができるので、二酸化炭素の還元反応を比較的低温に設定することができる。また、反応温度の上限を上記範囲に設定することにより、廃熱活用が容易になるばかりでなく、更なる経済性の向上を図ることができる。
なお、下限値と上限値とは、任意に組み合わせて、反応温度の範囲を規定することができる。 In addition, the reaction temperature (the contact temperature of the reducing agent with carbon dioxide) in the reduction reaction of carbon dioxide is preferably a temperature above 650°C, more preferably 700°C or higher, and 750°C or higher. is more preferable, and 800° C. or higher is particularly preferable. An efficient carbon dioxide reduction reaction can proceed within this temperature range.
The upper limit of the reaction temperature is preferably 1050° C. or lower, more preferably 1000° C. or lower, even more preferably 950° C. or lower, particularly preferably 900° C. or lower, and 850° C. or lower. Most preferably there is. Since the reducing agent can reduce carbon dioxide to carbon monoxide with high efficiency even at low temperatures, the reduction reaction of carbon dioxide can be set to a relatively low temperature. Further, by setting the upper limit of the reaction temperature within the above range, it is possible not only to facilitate utilization of waste heat, but also to further improve economic efficiency.
In addition, the lower limit and the upper limit can be arbitrarily combined to define the range of the reaction temperature.
また、二酸化炭素の還元反応の際、還元剤に接触させる二酸化炭素の量は、還元剤１ｇに対して１ｍｍｏｌ以上５０ｍｍｏｌ以下であることが好ましく、２．５ｍｍｏｌ以上３０ｍｍｏｌ以下であることがより好ましく、５ｍｍｏｌ以上２０ｍｍｏｌ以下であることがさらに好ましい。本発明の還元剤は、酸素元素の出入りが円滑になされる。このため、本発明の還元剤は、二酸化炭素の一酸化炭素への変換効率が高く（すなわち、一酸化炭素の生成量が多く）、かかる観点からも、二酸化炭素の削減に寄与する。一方、水素を含む還元ガスによって効率的に還元反応が行われるため、少ない水素量により還元剤を再生することができる。
本発明の還元剤における上記一酸化炭素の生成量は、還元剤１ｇに対して０．３ｍｍｏｌ以上１ｍｍｏｌ以下程度であることが好ましい。 In the carbon dioxide reduction reaction, the amount of carbon dioxide brought into contact with the reducing agent is preferably 1 mmol or more and 50 mmol or less, more preferably 2.5 mmol or more and 30 mmol or less, relative to 1 g of the reducing agent. More preferably, it is 5 mmol or more and 20 mmol or less. The reducing agent of the present invention facilitates entry and exit of oxygen element. Therefore, the reducing agent of the present invention has a high conversion efficiency of carbon dioxide to carbon monoxide (that is, a large amount of carbon monoxide is produced), and from this point of view also contributes to the reduction of carbon dioxide. On the other hand, since the reduction reaction is efficiently performed by the reducing gas containing hydrogen, the reducing agent can be regenerated with a small amount of hydrogen.
The amount of carbon monoxide produced in the reducing agent of the present invention is preferably about 0.3 mmol or more and 1 mmol or less per 1 g of the reducing agent.
本発明の還元剤における上記一酸化炭素の生成量は、還元剤１ｇに対して０．３ｍｍｏｌ以上１ｍｍｏｌ以下程度であることが好ましい。 In the carbon dioxide reduction reaction, the amount of carbon dioxide brought into contact with the reducing agent is preferably 1 mmol or more and 50 mmol or less, more preferably 2.5 mmol or more and 30 mmol or less, relative to 1 g of the reducing agent. More preferably, it is 5 mmol or more and 20 mmol or less. The reducing agent of the present invention facilitates entry and exit of oxygen element. Therefore, the reducing agent of the present invention has a high conversion efficiency of carbon dioxide to carbon monoxide (that is, a large amount of carbon monoxide is produced), and from this point of view also contributes to the reduction of carbon dioxide. On the other hand, since the reduction reaction is efficiently performed by the reducing gas containing hydrogen, the reducing agent can be regenerated with a small amount of hydrogen.
The amount of carbon monoxide produced in the reducing agent of the present invention is preferably about 0.3 mmol or more and 1 mmol or less per 1 g of the reducing agent.
なお、本発明では、二酸化炭素の還元反応で得られる還元物（炭素有価物）は、一酸化炭素を含むが、一酸化炭素以外の他の物質を含んでもよく、一酸化炭素と他の物質との混合物であってもよい。他の物質の具体例としては、例えば、メタンが挙げられる。上記二酸化炭素の還元反応で得られた一酸化炭素等の還元物は、さらに微生物発酵等により有機物質等に変換されることが好ましい。微生物発酵としては、嫌気性発酵が挙げられる。得られる有機物質としては、メタノール、エタノール、酢酸、ブタノール、これらの誘導体、またはこれらの混合物、イソプレン等のＣ５以上の化合物等が挙げられる。
さらに、一酸化炭素等の還元物は、金属酸化物等により、従来石油化学により合成される炭化水素、アルコールを含むＣ１からＣ２０までの化合物に変換されてもよい。得られる具体的な化合物としては、メタン、エタン、プロピレン、メタノール、エタノール、プロパノール、アセトアルデヒド、ジエチルエーテル、酢酸、酪酸、炭酸ジエチル、ブタジエン等が挙げられる。 In the present invention, the reduced product (carbon valuables) obtained by the reduction reaction of carbon dioxide contains carbon monoxide, but may contain substances other than carbon monoxide, and carbon monoxide and other substances It may be a mixture with Specific examples of other substances include, for example, methane. It is preferable that the reduced product such as carbon monoxide obtained by the carbon dioxide reduction reaction is further converted into an organic substance or the like by microbial fermentation or the like. Microbial fermentation includes anaerobic fermentation. Organic substances obtained include methanol, ethanol, acetic acid, butanol, derivatives thereof, mixtures thereof, and C5 or higher compounds such as isoprene.
Furthermore, the reduced products such as carbon monoxide may be converted into C1 to C20 compounds including hydrocarbons and alcohols conventionally synthesized by petrochemicals by metal oxides. Specific compounds obtained include methane, ethane, propylene, methanol, ethanol, propanol, acetaldehyde, diethyl ether, acetic acid, butyric acid, diethyl carbonate, butadiene, and the like.
さらに、一酸化炭素等の還元物は、金属酸化物等により、従来石油化学により合成される炭化水素、アルコールを含むＣ１からＣ２０までの化合物に変換されてもよい。得られる具体的な化合物としては、メタン、エタン、プロピレン、メタノール、エタノール、プロパノール、アセトアルデヒド、ジエチルエーテル、酢酸、酪酸、炭酸ジエチル、ブタジエン等が挙げられる。 In the present invention, the reduced product (carbon valuables) obtained by the reduction reaction of carbon dioxide contains carbon monoxide, but may contain substances other than carbon monoxide, and carbon monoxide and other substances It may be a mixture with Specific examples of other substances include, for example, methane. It is preferable that the reduced product such as carbon monoxide obtained by the carbon dioxide reduction reaction is further converted into an organic substance or the like by microbial fermentation or the like. Microbial fermentation includes anaerobic fermentation. Organic substances obtained include methanol, ethanol, acetic acid, butanol, derivatives thereof, mixtures thereof, and C5 or higher compounds such as isoprene.
Furthermore, the reduced products such as carbon monoxide may be converted into C1 to C20 compounds including hydrocarbons and alcohols conventionally synthesized by petrochemicals by metal oxides. Specific compounds obtained include methane, ethane, propylene, methanol, ethanol, propanol, acetaldehyde, diethyl ether, acetic acid, butyric acid, diethyl carbonate, butadiene, and the like.
［還元剤の特性］
本発明の還元剤は、次のような特性を有することが好ましい。
すなわち、流路内に圧力計を配置した内径８ｍｍのステンレス鋼製の反応管内に、還元剤を４０ｃｍの高さで充填し、濃度１００体積％の窒素ガスを３０ｍＬ／分で通過させたとき、１０分間での圧力上昇が０．０３ＭＰａＧ以下であることが好ましく、０．０１ＭＰａＧ以下であることがより好ましい。
かかる特性を示す還元剤は、充填密度および細孔容積が上記範囲を満たすと判断することができ、二酸化炭素の一酸化炭素への変換効率を十分に高めることができる。 [Characteristics of reducing agent]
The reducing agent of the present invention preferably has the following properties.
That is, when a reducing agent is filled at a height of 40 cm in a stainless steel reaction tube with an inner diameter of 8 mm and a pressure gauge is arranged in the flow channel, and nitrogen gas with a concentration of 100% by volume is passed at 30 mL / min, The pressure rise in 10 minutes is preferably 0.03 MPaG or less, more preferably 0.01 MPaG or less.
A reducing agent exhibiting such characteristics can be judged to satisfy the above ranges in packing density and pore volume, and can sufficiently increase the conversion efficiency of carbon dioxide to carbon monoxide.
本発明の還元剤は、次のような特性を有することが好ましい。
すなわち、流路内に圧力計を配置した内径８ｍｍのステンレス鋼製の反応管内に、還元剤を４０ｃｍの高さで充填し、濃度１００体積％の窒素ガスを３０ｍＬ／分で通過させたとき、１０分間での圧力上昇が０．０３ＭＰａＧ以下であることが好ましく、０．０１ＭＰａＧ以下であることがより好ましい。
かかる特性を示す還元剤は、充填密度および細孔容積が上記範囲を満たすと判断することができ、二酸化炭素の一酸化炭素への変換効率を十分に高めることができる。 [Characteristics of reducing agent]
The reducing agent of the present invention preferably has the following properties.
That is, when a reducing agent is filled at a height of 40 cm in a stainless steel reaction tube with an inner diameter of 8 mm and a pressure gauge is arranged in the flow channel, and nitrogen gas with a concentration of 100% by volume is passed at 30 mL / min, The pressure rise in 10 minutes is preferably 0.03 MPaG or less, more preferably 0.01 MPaG or less.
A reducing agent exhibiting such characteristics can be judged to satisfy the above ranges in packing density and pore volume, and can sufficiently increase the conversion efficiency of carbon dioxide to carbon monoxide.
以上のような本発明では、高温での反応に使用可能な還元剤、およびこの還元剤を使用したガスの製造方法を提供することができる。本発明の還元剤は、高温での使用に耐え得るため、高温でのケミカルルーピング反応により、二酸化炭素から一酸化炭素（炭素有価物）へのより効率のよい変換が可能となる。
With the present invention as described above, it is possible to provide a reducing agent that can be used in reactions at high temperatures, and a method for producing gas using this reducing agent. Since the reducing agent of the present invention can withstand use at high temperatures, chemical looping reactions at high temperatures enable more efficient conversion of carbon dioxide to carbon monoxide (carbon value).
さらに、次に記載の各態様で提供されてもよい。
In addition, it may be provided in each of the following aspects.
（１）接触により二酸化炭素を還元して炭素有価物を生成する還元剤であって、セリウム（Ｃｅ）およびセリウム（Ｃｅ）以外の遷移元素を含む金属酸化物で構成され、酸素イオン伝導性を備える酸素キャリアを含有し、前記酸素キャリアのＸ線回折測定を行ったとき、Ｘ線回折プロファイルにおいて、（２２０）面に対応する少なくとも１つの回折ピークのピーク位置が、酸化セリウム（ＣｅＯ２）の（２２０）面に対応する回折ピークのピーク位置に対してシフトしている、還元剤。
(1) A reducing agent that reduces carbon dioxide by contact to produce carbon valuables, is composed of cerium (Ce) and a metal oxide containing a transition element other than cerium (Ce), and has oxygen ion conductivity When X-ray diffraction measurement of the oxygen carrier is performed, the peak position of at least one diffraction peak corresponding to the (220) plane in the X-ray diffraction profile is that of cerium oxide (CeO 2 ) A reducing agent that is shifted with respect to the peak position of the diffraction peak corresponding to the (220) plane.
（２）上記（１）に記載の還元剤において、前記酸化セリウム（ＣｅＯ２）の（２２０）面に対応する回折ピークのピーク位置に対する、前記酸素キャリアの前記（２２０）面に対応する回折ピークのピーク位置のシフト量は、２θで０．１°以上０．６°未満である、還元剤。
(2) In the reducing agent described in (1) above, the diffraction peak corresponding to the (220) plane of the oxygen carrier with respect to the peak position of the diffraction peak corresponding to the (220) plane of the cerium oxide (CeO 2 ) The amount of shift of the peak position of is 0.1° or more and less than 0.6° in 2θ.
（３）上記（１）または（２）に記載の還元剤において、前記酸素キャリアの前記（２２０）面に対応する回折ピークは、その半値全幅が０．３以上である、還元剤。
(3) The reducing agent according to (1) or (2) above, wherein the diffraction peak corresponding to the (220) plane of the oxygen carrier has a full width at half maximum of 0.3 or more.
（４）上記（１）～（３）のいずれか１つに記載の還元剤において、前記酸素キャリアは、その結晶子サイズが３２０Å以下である、還元剤。
(4) The reducing agent according to any one of (1) to (3) above, wherein the oxygen carrier has a crystallite size of 320 Å or less.
（５）上記（１）～（４）のいずれか１つに記載の還元剤において、前記酸素キャリアの前記（２２０）面に対応する回折ピークにおいて、その半値全幅に対するピーク強度の比が６．２以下である、還元剤。
(5) In the reducing agent according to any one of (1) to (4) above, the diffraction peak corresponding to the (220) plane of the oxygen carrier has a peak intensity ratio to the full width at half maximum of 6.5. 2 or less, the reducing agent.
（６）上記（１）～（５）のいずれか１つに記載の還元剤において、前記遷移元素は、周期表の第４周期および第５周期に属する元素のうちの少なくとも１種である、還元剤。
(6) In the reducing agent according to any one of (1) to (5) above, the transition element is at least one element belonging to the fourth period and the fifth period of the periodic table. reducing agent.
（７）上記（１）～（６）のいずれか１つに記載の還元剤において、前記炭素有価物は、一酸化炭素を含む、還元剤。
(7) The reducing agent according to any one of (1) to (6) above, wherein the carbon valuables include carbon monoxide.
（８）上記（１）～（７）のいずれか１つに記載の還元剤において、前記二酸化炭素との接触は、６５０℃を上回る温度で行われる、還元剤。
(8) The reducing agent according to any one of (1) to (7) above, wherein the contact with carbon dioxide is carried out at a temperature above 650°C.
（９）上記（１）～（８）のいずれか１つに記載の還元剤において、前記二酸化炭素との接触により酸化された前記還元剤は、水素を含む還元ガスと接触させることにより還元される、還元剤。
(9) In the reducing agent according to any one of (1) to (8) above, the reducing agent oxidized by contact with carbon dioxide is reduced by contact with a reducing gas containing hydrogen. , reducing agent.
（１０）上記（９）に記載の還元剤において、前記水素を含む還元ガスとの接触は、６５０℃を上回る温度で行われる、還元剤。
(10) The reducing agent according to (9) above, wherein the contact with the reducing gas containing hydrogen is performed at a temperature above 650°C.
（１１）上記（９）または（１０）に記載の還元剤において前記水素を含む還元ガスと接触させることにより、前記還元剤に含まれる前記酸素キャリアの質量に対して０．４５％以上の可逆的な酸素欠損量を生じる、還元剤。
(11) By contacting the reducing gas containing hydrogen in the reducing agent according to (9) or (10) above, a reversible oxygen carrier content of 0.45% or more with respect to the mass of the oxygen carrier contained in the reducing agent is obtained. A reducing agent that produces a significant amount of oxygen deficiency.
（１２）上記（１）～（１１）のいずれか１つに記載の還元剤において、さらに、前記酸素キャリアを結合する結合剤を含有する、還元剤。
(12) The reducing agent according to any one of (1) to (11) above, further comprising a binder that binds the oxygen carrier.
（１３）上記（１２）に記載の還元剤において、前記還元剤に含まれる前記結合剤の割合は、前記還元剤１００質量部に対して１質量部以上６０質量部以下である、還元剤。
(13) The reducing agent according to (12) above, wherein the ratio of the binder contained in the reducing agent is 1 part by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the reducing agent.
（１４）二酸化炭素を含む原料ガスを還元剤と接触させることにより、前記二酸化炭素を還元して炭素有価物を含む生成ガスを製造するガスの製造方法であって、前記還元剤は、セリウム（Ｃｅ）およびセリウム（Ｃｅ）以外の遷移元素を含む金属酸化物で構成され、酸素イオン伝導性を備える酸素キャリアを含有し、前記酸素キャリアのＸ線回折測定を行ったとき、Ｘ線回折プロファイルにおいて、（２２０）面に対応する少なくとも１つの回折ピークのピーク位置が、酸化セリウム（ＣｅＯ２）の（２２０）面に対応する回折ピークのピーク位置に対してシフトしている、ガスの製造方法。
もちろん、この限りではない。 (14) A gas production method for producing a product gas containing carbon valuables by reducing the carbon dioxide by bringing a raw material gas containing carbon dioxide into contact with a reducing agent, wherein the reducing agent is cerium ( Ce) and a metal oxide containing a transition element other than cerium (Ce), contains an oxygen carrier having oxygen ion conductivity, and when the oxygen carrier is subjected to X-ray diffraction measurement, the X-ray diffraction profile shows , the peak position of at least one diffraction peak corresponding to the (220) plane is shifted with respect to the peak position of the diffraction peak corresponding to the (220) plane of cerium oxide (CeO 2 ).
Of course, this is not the only case.
もちろん、この限りではない。 (14) A gas production method for producing a product gas containing carbon valuables by reducing the carbon dioxide by bringing a raw material gas containing carbon dioxide into contact with a reducing agent, wherein the reducing agent is cerium ( Ce) and a metal oxide containing a transition element other than cerium (Ce), contains an oxygen carrier having oxygen ion conductivity, and when the oxygen carrier is subjected to X-ray diffraction measurement, the X-ray diffraction profile shows , the peak position of at least one diffraction peak corresponding to the (220) plane is shifted with respect to the peak position of the diffraction peak corresponding to the (220) plane of cerium oxide (CeO 2 ).
Of course, this is not the only case.
既述のとおり、本発明に係る種々の実施形態を説明したが、これらは、例として提示したものであり、発明の範囲を何ら限定するものではない。当該新規な実施形態は、その他の様々な形態で実施されることが可能であり、発明の要旨を逸脱しない範囲で、種々の省略、置き換え、変更を行うことができる。当該実施形態やその変形は、発明の範囲や要旨に含まれるとともに、特許請求の範囲に記載された発明とその均等の範囲に含まれるものである。
As described above, various embodiments of the present invention have been described, but these are presented as examples and do not limit the scope of the invention in any way. The novel embodiment can be embodied in various other forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. The embodiment and its modifications are included in the scope and gist of the invention, and are included in the scope of the invention described in the claims and equivalents thereof.
例えば、本発明の還元剤およびガスの製造方法は、上記実施形態に対して、他の任意の追加の構成を有していてもよく、同様の機能を発揮する任意の構成と置換されていてよく、一部の構成が省略されていてもよい。
上記実施形態では、還元ガスとして水素を含むガスを代表に説明したが、還元ガスには、還元物質として、水素に代えてまたは水素に加えて、炭化水素（例えば、メタン、エタン、アセチレン等）およびアンモニアから選択される少なくとも１種を含むガスを使用することもできる。 For example, the method for producing a reducing agent and gas of the present invention may have any other configuration added to the above embodiments, and may be replaced with any configuration that performs similar functions. Well, part of the configuration may be omitted.
In the above embodiments, a gas containing hydrogen was described as a representative example of the reducing gas. However, the reducing gas includes a hydrocarbon (eg, methane, ethane, acetylene, etc.) as a reducing substance instead of or in addition to hydrogen. and ammonia can also be used.
上記実施形態では、還元ガスとして水素を含むガスを代表に説明したが、還元ガスには、還元物質として、水素に代えてまたは水素に加えて、炭化水素（例えば、メタン、エタン、アセチレン等）およびアンモニアから選択される少なくとも１種を含むガスを使用することもできる。 For example, the method for producing a reducing agent and gas of the present invention may have any other configuration added to the above embodiments, and may be replaced with any configuration that performs similar functions. Well, part of the configuration may be omitted.
In the above embodiments, a gas containing hydrogen was described as a representative example of the reducing gas. However, the reducing gas includes a hydrocarbon (eg, methane, ethane, acetylene, etc.) as a reducing substance instead of or in addition to hydrogen. and ammonia can also be used.
以下に、実施例および比較例を挙げて、本発明をさらに具体的に説明するが、本発明は、これらの実施例に限定されるものではない。
The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.
１．還元剤の製造
（実施例１）
まず、酸化セリウム（株式会社高純度化学社製）と、酸化マンガン（ＩＶ）（富士フイルム和光純薬工業株式会社製）と、酸化鉄（ＩＩＩ）（富士フイルム和光純薬工業株式会社製）とを、それぞれ所定量を計量した。次に、計量した各酸化物の粒子と、イオン交換水１００ｍＬと、４ｍｍΦのジルコニアビーズとを、ジルコニア製の容器に収納した。その後、これらを、ジルコニアビーズを用いて４００ｒｐｍの回転数で２４時間粉砕した後、１２０℃で乾燥させた。なお、酸化セリウムと酸化マンガンと酸化鉄とのモル比を０．９４：０．０４：０．０２とした。 1. Production of reducing agent (Example 1)
First, cerium oxide (manufactured by Kojundo Chemical Co., Ltd.), manganese (IV) oxide (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), and iron oxide (III) (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) were weighed out in predetermined amounts. Next, the weighed particles of each oxide, 100 mL of deionized water, and zirconia beads of 4 mmΦ were placed in a zirconia container. After that, they were pulverized with zirconia beads at a rotation speed of 400 rpm for 24 hours, and then dried at 120°C. The molar ratio of cerium oxide, manganese oxide and iron oxide was 0.94:0.04:0.02.
（実施例１）
まず、酸化セリウム（株式会社高純度化学社製）と、酸化マンガン（ＩＶ）（富士フイルム和光純薬工業株式会社製）と、酸化鉄（ＩＩＩ）（富士フイルム和光純薬工業株式会社製）とを、それぞれ所定量を計量した。次に、計量した各酸化物の粒子と、イオン交換水１００ｍＬと、４ｍｍΦのジルコニアビーズとを、ジルコニア製の容器に収納した。その後、これらを、ジルコニアビーズを用いて４００ｒｐｍの回転数で２４時間粉砕した後、１２０℃で乾燥させた。なお、酸化セリウムと酸化マンガンと酸化鉄とのモル比を０．９４：０．０４：０．０２とした。 1. Production of reducing agent (Example 1)
First, cerium oxide (manufactured by Kojundo Chemical Co., Ltd.), manganese (IV) oxide (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), and iron oxide (III) (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) were weighed out in predetermined amounts. Next, the weighed particles of each oxide, 100 mL of deionized water, and zirconia beads of 4 mmΦ were placed in a zirconia container. After that, they were pulverized with zirconia beads at a rotation speed of 400 rpm for 24 hours, and then dried at 120°C. The molar ratio of cerium oxide, manganese oxide and iron oxide was 0.94:0.04:0.02.
得られた酸化物の塊状物を粉砕し、大気雰囲気下で、室温から４５０℃まで８℃／分の速度で昇温した後、４５０℃で４時間焼成した。その後、さらに９５０℃まで８℃／分の速度で昇温した後、９５０℃で８時間焼成した。最後に、焼成した塊状物を機械的に細かく粉砕した。これにより、目的とする酸素キャリア単独で構成される還元剤を得た。なお、還元剤は粒状であった。
The resulting oxide mass was pulverized, heated from room temperature to 450°C at a rate of 8°C/min in an air atmosphere, and then fired at 450°C for 4 hours. After that, the temperature was further raised to 950° C. at a rate of 8° C./min, and then fired at 950° C. for 8 hours. Finally, the calcined mass was finely ground mechanically. As a result, the desired reducing agent composed solely of the oxygen carrier was obtained. The reducing agent was granular.
（実施例２）
２４時間の粉砕を２０時間の粉砕に変更した以外は、実施例１と同様にして、還元剤を製造した。 (Example 2)
A reducing agent was produced in the same manner as in Example 1, except that the 24-hour pulverization was changed to 20-hour pulverization.
２４時間の粉砕を２０時間の粉砕に変更した以外は、実施例１と同様にして、還元剤を製造した。 (Example 2)
A reducing agent was produced in the same manner as in Example 1, except that the 24-hour pulverization was changed to 20-hour pulverization.
（実施例３）
まず、還元剤の前駆体として、硝酸セリウム（ＩＩＩ）六水和物（富士フイルム和光純薬工業株式会社製、純度：９８．０％）と、硝酸ジルコニウム二水和物（富士フイルム和光純薬工業株式会社製、純度：９７．０％）と、硝酸サマリウム六水和物（富士フイルム和光純薬工業株式会社製、純度：９９．５％）と、硝酸鉄（ＩＩＩ）九水和物（富士フイルム和光純薬工業株式会社製、純度：９９．９％）と硝酸銅（ＩＩ）三水和物（富士フイルム和光純薬工業株式会社製、純度：９９．０％）を、それぞれ所定量を計量した。 (Example 3)
First, as precursors of the reducing agent, cerium (III) nitrate hexahydrate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., purity: 98.0%) and zirconium nitrate dihydrate (FUJIFILM Wako Pure Chemical Industries, Ltd. Industrial Co., Ltd., purity: 97.0%), samarium nitrate hexahydrate (Fujifilm Wako Pure Chemical Industries, Ltd., purity: 99.5%), and iron (III) nitrate nonahydrate ( Manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purity: 99.9%) and copper (II) nitrate trihydrate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., purity: 99.0%). was weighed.
まず、還元剤の前駆体として、硝酸セリウム（ＩＩＩ）六水和物（富士フイルム和光純薬工業株式会社製、純度：９８．０％）と、硝酸ジルコニウム二水和物（富士フイルム和光純薬工業株式会社製、純度：９７．０％）と、硝酸サマリウム六水和物（富士フイルム和光純薬工業株式会社製、純度：９９．５％）と、硝酸鉄（ＩＩＩ）九水和物（富士フイルム和光純薬工業株式会社製、純度：９９．９％）と硝酸銅（ＩＩ）三水和物（富士フイルム和光純薬工業株式会社製、純度：９９．０％）を、それぞれ所定量を計量した。 (Example 3)
First, as precursors of the reducing agent, cerium (III) nitrate hexahydrate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., purity: 98.0%) and zirconium nitrate dihydrate (FUJIFILM Wako Pure Chemical Industries, Ltd. Industrial Co., Ltd., purity: 97.0%), samarium nitrate hexahydrate (Fujifilm Wako Pure Chemical Industries, Ltd., purity: 99.5%), and iron (III) nitrate nonahydrate ( Manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purity: 99.9%) and copper (II) nitrate trihydrate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., purity: 99.0%). was weighed.
次いで、６．０６ｇのクエン酸（富士フイルム和光純薬工業株式会社製、純度：９９．５％）を計量し、９６ｍＬの脱イオン水に溶解してクエン酸水溶液を得た。その後、上記前駆体（硝酸金属塩）を、攪拌しつつクエン酸水溶液に室温で添加して、前駆体水溶液を調製した。なお、前駆体水溶液中におけるＣｅ：Ｚｒ＋Ｓｍ＋Ｆｅ＋Ｃｕ（モル比）を、０．７０：０．３０とした。
３０分経過後、全金属塩の２．４モル等量のエチレングリコール（富士フイルム和光純薬工業株式会社製、純度：９９．５％）を前駆体水溶液に添加し、温度を８０℃に上昇させた。 Next, 6.06 g of citric acid (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd., purity: 99.5%) was weighed and dissolved in 96 mL of deionized water to obtain an aqueous citric acid solution. Thereafter, the above precursor (metal nitrate) was added to the aqueous citric acid solution at room temperature while stirring to prepare an aqueous precursor solution. The Ce:Zr+Sm+Fe+Cu (molar ratio) in the precursor aqueous solution was set to 0.70:0.30.
After 30 minutes, ethylene glycol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purity: 99.5%) of 2.4 molar equivalents of all metal salts was added to the aqueous precursor solution, and the temperature was raised to 80°C. let me
３０分経過後、全金属塩の２．４モル等量のエチレングリコール（富士フイルム和光純薬工業株式会社製、純度：９９．５％）を前駆体水溶液に添加し、温度を８０℃に上昇させた。 Next, 6.06 g of citric acid (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd., purity: 99.5%) was weighed and dissolved in 96 mL of deionized water to obtain an aqueous citric acid solution. Thereafter, the above precursor (metal nitrate) was added to the aqueous citric acid solution at room temperature while stirring to prepare an aqueous precursor solution. The Ce:Zr+Sm+Fe+Cu (molar ratio) in the precursor aqueous solution was set to 0.70:0.30.
After 30 minutes, ethylene glycol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purity: 99.5%) of 2.4 molar equivalents of all metal salts was added to the aqueous precursor solution, and the temperature was raised to 80°C. let me
粘性のゲルが形成されるまで、連続して撹拌しつつ、８０℃の温度を維持した。その後、ゲルを乾燥炉へ移動させた。
ゲルの乾燥は、１２０℃、５時間で行った。
生成された有機および無機化合物の膨潤した塊状物を粉砕し、大気雰囲気下で、室温から４５０℃まで８℃／分の速度で昇温した後、４５０℃で４時間焼成した。その後、さらに９５０℃まで８℃／分の速度で昇温した後、９５０℃で８時間焼成した。
最後に、焼成した塊状物を機械的に細かく粉砕した。これにより、目的とする酸素キャリア単独で構成される還元剤を得た。なお、還元剤は粒状であった。 A temperature of 80° C. was maintained with continuous stirring until a viscous gel was formed. After that, the gel was transferred to a drying oven.
Drying of the gel was performed at 120° C. for 5 hours.
The resulting swollen lumps of organic and inorganic compounds were pulverized, heated from room temperature to 450° C. at a rate of 8° C./min, and then calcined at 450° C. for 4 hours. After that, the temperature was further raised to 950° C. at a rate of 8° C./min, and then fired at 950° C. for 8 hours.
Finally, the calcined mass was finely ground mechanically. As a result, the desired reducing agent composed solely of the oxygen carrier was obtained. The reducing agent was granular.
ゲルの乾燥は、１２０℃、５時間で行った。
生成された有機および無機化合物の膨潤した塊状物を粉砕し、大気雰囲気下で、室温から４５０℃まで８℃／分の速度で昇温した後、４５０℃で４時間焼成した。その後、さらに９５０℃まで８℃／分の速度で昇温した後、９５０℃で８時間焼成した。
最後に、焼成した塊状物を機械的に細かく粉砕した。これにより、目的とする酸素キャリア単独で構成される還元剤を得た。なお、還元剤は粒状であった。 A temperature of 80° C. was maintained with continuous stirring until a viscous gel was formed. After that, the gel was transferred to a drying oven.
Drying of the gel was performed at 120° C. for 5 hours.
The resulting swollen lumps of organic and inorganic compounds were pulverized, heated from room temperature to 450° C. at a rate of 8° C./min, and then calcined at 450° C. for 4 hours. After that, the temperature was further raised to 950° C. at a rate of 8° C./min, and then fired at 950° C. for 8 hours.
Finally, the calcined mass was finely ground mechanically. As a result, the desired reducing agent composed solely of the oxygen carrier was obtained. The reducing agent was granular.
（実施例４）
還元剤の前駆体の種類を変更した以外は、実施例３と同様にして、還元剤を製造した。
還元剤の前駆体として、硝酸セリウム（ＩＩＩ）六水和物（富士フイルム和光純薬工業株式会社製、純度：９８．０％）と、硝酸ジルコニウム二水和物（富士フイルム和光純薬工業株式会社製、純度：９７．０％）と、硝酸ランタン（ＩＩＩ）六水和物（富士フイルム和光純薬工業株式会社製、純度：９９．９％）と、３０％硫酸チタン（ＩＶ）溶液（富士フイルム和光純薬工業株式会社製）と、硝酸鉄（ＩＩＩ）九水和物（富士フイルム和光純薬工業株式会社製、純度：９９．９％）を、それぞれ所定量を計量した。
なお、前駆体水溶液中におけるＣｅ：Ｚｒ＋Ｌａ＋Ｔｉ＋Ｆｅ（モル比）を、０．６４：０．３６とした。 (Example 4)
A reducing agent was produced in the same manner as in Example 3, except that the type of precursor of the reducing agent was changed.
As precursors of the reducing agent, cerium (III) nitrate hexahydrate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., purity: 98.0%) and zirconium nitrate dihydrate (FUJIFILM Wako Pure Chemical Industries, Ltd. company, purity: 97.0%), lanthanum (III) nitrate hexahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purity: 99.9%), and 30% titanium (IV) sulfate solution ( FUJIFILM Wako Pure Chemical Industries, Ltd.) and iron (III) nitrate nonahydrate (FUJIFILM Wako Pure Chemical Industries, Ltd., purity: 99.9%) were weighed in predetermined amounts.
The Ce:Zr+La+Ti+Fe (molar ratio) in the precursor aqueous solution was set to 0.64:0.36.
還元剤の前駆体の種類を変更した以外は、実施例３と同様にして、還元剤を製造した。
還元剤の前駆体として、硝酸セリウム（ＩＩＩ）六水和物（富士フイルム和光純薬工業株式会社製、純度：９８．０％）と、硝酸ジルコニウム二水和物（富士フイルム和光純薬工業株式会社製、純度：９７．０％）と、硝酸ランタン（ＩＩＩ）六水和物（富士フイルム和光純薬工業株式会社製、純度：９９．９％）と、３０％硫酸チタン（ＩＶ）溶液（富士フイルム和光純薬工業株式会社製）と、硝酸鉄（ＩＩＩ）九水和物（富士フイルム和光純薬工業株式会社製、純度：９９．９％）を、それぞれ所定量を計量した。
なお、前駆体水溶液中におけるＣｅ：Ｚｒ＋Ｌａ＋Ｔｉ＋Ｆｅ（モル比）を、０．６４：０．３６とした。 (Example 4)
A reducing agent was produced in the same manner as in Example 3, except that the type of precursor of the reducing agent was changed.
As precursors of the reducing agent, cerium (III) nitrate hexahydrate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., purity: 98.0%) and zirconium nitrate dihydrate (FUJIFILM Wako Pure Chemical Industries, Ltd. company, purity: 97.0%), lanthanum (III) nitrate hexahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purity: 99.9%), and 30% titanium (IV) sulfate solution ( FUJIFILM Wako Pure Chemical Industries, Ltd.) and iron (III) nitrate nonahydrate (FUJIFILM Wako Pure Chemical Industries, Ltd., purity: 99.9%) were weighed in predetermined amounts.
The Ce:Zr+La+Ti+Fe (molar ratio) in the precursor aqueous solution was set to 0.64:0.36.
（実施例５）
還元剤の前駆体の種類を変更した以外は、実施例３と同様にして、還元剤を製造した。
還元剤の前駆体として、硝酸セリウム（ＩＩＩ）六水和物（富士フイルム和光純薬工業株式会社製、純度：９８．０％）と、硝酸ジルコニウム二水和物（富士フイルム和光純薬工業株式会社製、純度：９７．０％）と、硝酸ニッケル（ＩＩ）六水和物（富士フイルム和光純薬工業株式会社製、純度：９９．９％）を、それぞれ所定量を計量した。
なお、前駆体水溶液中におけるＣｅ：Ｚｒ：Ｎｉ（モル比）を、０．９０：０．０８：０．０２とした。 (Example 5)
A reducing agent was produced in the same manner as in Example 3, except that the type of precursor of the reducing agent was changed.
As precursors of the reducing agent, cerium (III) nitrate hexahydrate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., purity: 98.0%) and zirconium nitrate dihydrate (FUJIFILM Wako Pure Chemical Industries, Ltd. company, purity: 97.0%) and nickel (II) nitrate hexahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purity: 99.9%) were weighed in predetermined amounts.
The Ce:Zr:Ni (molar ratio) in the precursor aqueous solution was set to 0.90:0.08:0.02.
還元剤の前駆体の種類を変更した以外は、実施例３と同様にして、還元剤を製造した。
還元剤の前駆体として、硝酸セリウム（ＩＩＩ）六水和物（富士フイルム和光純薬工業株式会社製、純度：９８．０％）と、硝酸ジルコニウム二水和物（富士フイルム和光純薬工業株式会社製、純度：９７．０％）と、硝酸ニッケル（ＩＩ）六水和物（富士フイルム和光純薬工業株式会社製、純度：９９．９％）を、それぞれ所定量を計量した。
なお、前駆体水溶液中におけるＣｅ：Ｚｒ：Ｎｉ（モル比）を、０．９０：０．０８：０．０２とした。 (Example 5)
A reducing agent was produced in the same manner as in Example 3, except that the type of precursor of the reducing agent was changed.
As precursors of the reducing agent, cerium (III) nitrate hexahydrate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., purity: 98.0%) and zirconium nitrate dihydrate (FUJIFILM Wako Pure Chemical Industries, Ltd. company, purity: 97.0%) and nickel (II) nitrate hexahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purity: 99.9%) were weighed in predetermined amounts.
The Ce:Zr:Ni (molar ratio) in the precursor aqueous solution was set to 0.90:0.08:0.02.
（実施例６）
還元剤の前駆体の種類を変更した以外は、実施例３と同様にして、還元剤を製造した。
還元剤の前駆体として、硝酸セリウム（ＩＩＩ）六水和物（富士フイルム和光純薬工業株式会社製、純度：９８．０％）と、硝酸ジルコニウム二水和物（富士フイルム和光純薬工業株式会社製、純度：９７．０％）と、シュウ酸アンモニウムニオビウム（シグマアルドリッチ、純度：９９．９９％）を、それぞれ所定量を計量した。
なお、前駆体水溶液中におけるＣｅ：Ｚｒ：Ｎｂ（モル比）を、０．９０：０．０８：０．０２とした。 (Example 6)
A reducing agent was produced in the same manner as in Example 3, except that the type of precursor of the reducing agent was changed.
As precursors of the reducing agent, cerium (III) nitrate hexahydrate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., purity: 98.0%) and zirconium nitrate dihydrate (FUJIFILM Wako Pure Chemical Industries, Ltd. Predetermined amounts of ammonium niobium oxalate (Sigma-Aldrich, purity: 97.0%) and niobium ammonium oxalate (purity: 99.99%) were weighed.
The Ce:Zr:Nb (molar ratio) in the precursor aqueous solution was set to 0.90:0.08:0.02.
還元剤の前駆体の種類を変更した以外は、実施例３と同様にして、還元剤を製造した。
還元剤の前駆体として、硝酸セリウム（ＩＩＩ）六水和物（富士フイルム和光純薬工業株式会社製、純度：９８．０％）と、硝酸ジルコニウム二水和物（富士フイルム和光純薬工業株式会社製、純度：９７．０％）と、シュウ酸アンモニウムニオビウム（シグマアルドリッチ、純度：９９．９９％）を、それぞれ所定量を計量した。
なお、前駆体水溶液中におけるＣｅ：Ｚｒ：Ｎｂ（モル比）を、０．９０：０．０８：０．０２とした。 (Example 6)
A reducing agent was produced in the same manner as in Example 3, except that the type of precursor of the reducing agent was changed.
As precursors of the reducing agent, cerium (III) nitrate hexahydrate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., purity: 98.0%) and zirconium nitrate dihydrate (FUJIFILM Wako Pure Chemical Industries, Ltd. Predetermined amounts of ammonium niobium oxalate (Sigma-Aldrich, purity: 97.0%) and niobium ammonium oxalate (purity: 99.99%) were weighed.
The Ce:Zr:Nb (molar ratio) in the precursor aqueous solution was set to 0.90:0.08:0.02.
（実施例７）
還元剤の前駆体の種類を変更した以外は、実施例３と同様にして、還元剤を製造した。
還元剤の前駆体として、硝酸セリウム（ＩＩＩ）六水和物（富士フイルム和光純薬工業株式会社製、純度：９８．０％）と、３０％硫酸チタン（ＩＶ）溶液（富士フイルム和光純薬工業株式会社製）と、硝酸ランタン（ＩＩＩ）六水和物（富士フイルム和光純薬工業株式会社製、純度：９９．９％）を、それぞれ所定量を計量した。
なお、前駆体水溶液中におけるＣｅ：Ｔｉ：Ｌａ（モル比）を、０．５８：０．２５：０．１７とした。 (Example 7)
A reducing agent was produced in the same manner as in Example 3, except that the type of precursor of the reducing agent was changed.
As precursors of the reducing agent, cerium (III) nitrate hexahydrate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., purity: 98.0%) and 30% titanium (IV) sulfate solution (FUJIFILM Wako Pure Chemical Industries, Ltd. Kogyo Co., Ltd.) and lanthanum (III) nitrate hexahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purity: 99.9%) were weighed in predetermined amounts.
The Ce:Ti:La (molar ratio) in the precursor aqueous solution was set to 0.58:0.25:0.17.
還元剤の前駆体の種類を変更した以外は、実施例３と同様にして、還元剤を製造した。
還元剤の前駆体として、硝酸セリウム（ＩＩＩ）六水和物（富士フイルム和光純薬工業株式会社製、純度：９８．０％）と、３０％硫酸チタン（ＩＶ）溶液（富士フイルム和光純薬工業株式会社製）と、硝酸ランタン（ＩＩＩ）六水和物（富士フイルム和光純薬工業株式会社製、純度：９９．９％）を、それぞれ所定量を計量した。
なお、前駆体水溶液中におけるＣｅ：Ｔｉ：Ｌａ（モル比）を、０．５８：０．２５：０．１７とした。 (Example 7)
A reducing agent was produced in the same manner as in Example 3, except that the type of precursor of the reducing agent was changed.
As precursors of the reducing agent, cerium (III) nitrate hexahydrate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., purity: 98.0%) and 30% titanium (IV) sulfate solution (FUJIFILM Wako Pure Chemical Industries, Ltd. Kogyo Co., Ltd.) and lanthanum (III) nitrate hexahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., purity: 99.9%) were weighed in predetermined amounts.
The Ce:Ti:La (molar ratio) in the precursor aqueous solution was set to 0.58:0.25:0.17.
（実施例８）
実施例３で得られた酸素キャリアに対して、結合剤として酸化アルミニウム（富士フイルム和光純薬工業株式会社製、和光特級）を秤量して、乳鉢で１０分間混合した。その後、大気雰囲気下で、室温から９５０℃まで８℃／分の速度で昇温した後、９５０℃で８時間焼成した。これにより、還元剤を得た。
なお、還元剤に含まれる酸化アルミニウムの割合は、還元剤１００質量部に対して１０質量部とした。 (Example 8)
Aluminum oxide (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd., special grade Wako) was weighed as a binder to the oxygen carrier obtained in Example 3, and mixed in a mortar for 10 minutes. After that, the temperature was raised from room temperature to 950° C. at a rate of 8° C./min in an air atmosphere, and then fired at 950° C. for 8 hours. Thus, a reducing agent was obtained.
The ratio of aluminum oxide contained in the reducing agent was 10 parts by mass with respect to 100 parts by mass of the reducing agent.
実施例３で得られた酸素キャリアに対して、結合剤として酸化アルミニウム（富士フイルム和光純薬工業株式会社製、和光特級）を秤量して、乳鉢で１０分間混合した。その後、大気雰囲気下で、室温から９５０℃まで８℃／分の速度で昇温した後、９５０℃で８時間焼成した。これにより、還元剤を得た。
なお、還元剤に含まれる酸化アルミニウムの割合は、還元剤１００質量部に対して１０質量部とした。 (Example 8)
Aluminum oxide (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd., special grade Wako) was weighed as a binder to the oxygen carrier obtained in Example 3, and mixed in a mortar for 10 minutes. After that, the temperature was raised from room temperature to 950° C. at a rate of 8° C./min in an air atmosphere, and then fired at 950° C. for 8 hours. Thus, a reducing agent was obtained.
The ratio of aluminum oxide contained in the reducing agent was 10 parts by mass with respect to 100 parts by mass of the reducing agent.
（比較例１）
酸化セリウム単体を打錠することにより還元剤を得た。
なお、実施例１～３で得られた還元剤の充填密度は、２ｇ／ｍＬ以上２．５ｇ／ｍＬ以下であった。 (Comparative example 1)
A reducing agent was obtained by tableting cerium oxide alone.
The packing densities of the reducing agents obtained in Examples 1 to 3 were 2 g/mL or more and 2.5 g/mL or less.
酸化セリウム単体を打錠することにより還元剤を得た。
なお、実施例１～３で得られた還元剤の充填密度は、２ｇ／ｍＬ以上２．５ｇ／ｍＬ以下であった。 (Comparative example 1)
A reducing agent was obtained by tableting cerium oxide alone.
The packing densities of the reducing agents obtained in Examples 1 to 3 were 2 g/mL or more and 2.5 g/mL or less.
２．還元剤の同定
還元剤（金属酸化物）中の金属組成は、ＡＭＥＴＥＫ社製のＳＰＥＣＴＲＯ ＡＲＣＯＳを用いてアルゴンガスによるＩＣＰ発光分光分析法により分析、同定した。
測定溶液は、以下の手法により調製した。還元剤５０～１００ｍｇを１％硝酸ないし１％フッ酸１００ｍＬに溶解させ、得られた溶液をさらに１０倍に希釈した。
上記測定溶液を分析した結果（金属元素のモル比）を表１に示す。 2. Identification of Reducing Agent The metal composition in the reducing agent (metal oxide) was analyzed and identified by ICP emission spectrometry using argon gas using SPECTRO ARCOS manufactured by AMETEK.
A measurement solution was prepared by the following method. 50 to 100 mg of a reducing agent was dissolved in 100 mL of 1% nitric acid to 1% hydrofluoric acid, and the obtained solution was further diluted 10 times.
Table 1 shows the results (molar ratios of metal elements) of the analysis of the measurement solution.
還元剤（金属酸化物）中の金属組成は、ＡＭＥＴＥＫ社製のＳＰＥＣＴＲＯ ＡＲＣＯＳを用いてアルゴンガスによるＩＣＰ発光分光分析法により分析、同定した。
測定溶液は、以下の手法により調製した。還元剤５０～１００ｍｇを１％硝酸ないし１％フッ酸１００ｍＬに溶解させ、得られた溶液をさらに１０倍に希釈した。
上記測定溶液を分析した結果（金属元素のモル比）を表１に示す。 2. Identification of Reducing Agent The metal composition in the reducing agent (metal oxide) was analyzed and identified by ICP emission spectrometry using argon gas using SPECTRO ARCOS manufactured by AMETEK.
A measurement solution was prepared by the following method. 50 to 100 mg of a reducing agent was dissolved in 100 mL of 1% nitric acid to 1% hydrofluoric acid, and the obtained solution was further diluted 10 times.
Table 1 shows the results (molar ratios of metal elements) of the analysis of the measurement solution.
３．粒度分布の測定
粒度分布測定装置（堀場製作所製、「ＬＡ－９６０Ｓ」）を使用して、還元剤の粒度分布を測定した。なお、溶媒には水を使用して、測定は透過率が７０％以上の状態で行った。
その結果、還元剤の体積基準５０％径は、いずれも５０μｍ以下であった。 3. Measurement of Particle Size Distribution The particle size distribution of the reducing agent was measured using a particle size distribution analyzer ("LA-960S" manufactured by Horiba, Ltd.). Water was used as a solvent, and the measurement was performed in a state where the transmittance was 70% or more.
As a result, the volume-based 50% diameters of the reducing agents were all 50 μm or less.
粒度分布測定装置（堀場製作所製、「ＬＡ－９６０Ｓ」）を使用して、還元剤の粒度分布を測定した。なお、溶媒には水を使用して、測定は透過率が７０％以上の状態で行った。
その結果、還元剤の体積基準５０％径は、いずれも５０μｍ以下であった。 3. Measurement of Particle Size Distribution The particle size distribution of the reducing agent was measured using a particle size distribution analyzer ("LA-960S" manufactured by Horiba, Ltd.). Water was used as a solvent, and the measurement was performed in a state where the transmittance was 70% or more.
As a result, the volume-based 50% diameters of the reducing agents were all 50 μm or less.
４．Ｘ線回折測定
Ｘ線回折測定を行う前に、還元剤のサンプル調製を行った。
まず、１００ｍｇ程度の還元剤を乳鉢に計り取り、乳棒を用いて磨り潰した。その後、還元剤を試料板の試料充填部の穴に均一に充填し、試料板の表面と還元剤による表面が同一面になるように調整した。
Ｘ線回折測定には、Ｘ線回折装置（株式会社Ｂｒｕｋｅｒ社製、「Ｄ８ ＤＩＳＣＯＶＥＲ」）を使用し、集中法により測定を実施した。対陰極には、純銅を用いた銅管球を用い、ＣｕＫαの特性Ｘ線（Ｋα１の波長（λ）＝１．５４０５６Å（０．１５４０５６ｎｍ）、Ｋα２の波長（λ）＝１．５４４３９Å（０．１５４４３９ｎｍ）、Ｋα２の比率＝０．５００００）を回折に使用した。
回折計は、発散スリットを１／２°、発散縦制限スリットを１０ｍｍ、散乱スリットを２°、受光スリット０．１５ｍｍに設定した。ゴニオメーター半径は１６９．３ｍｍであった。 4. X-Ray Diffraction Measurement Before X-ray diffraction measurement, a reducing agent sample was prepared.
First, about 100 mg of reducing agent was weighed into a mortar and ground with a pestle. After that, the reducing agent was uniformly filled into the holes of the sample filling portion of the sample plate, and the surface of the sample plate and the surface of the reducing agent were adjusted to be flush with each other.
For the X-ray diffraction measurement, an X-ray diffractometer ("D8 DISCOVER" manufactured by Bruker Co., Ltd.) was used, and the measurement was performed by the concentration method. A copper tube using pure copper was used as the anticathode, and characteristic X-rays of CuKα (wavelength (λ) of Kα1 = 1.54056 Å (0.154056 nm), wavelength (λ) of Kα2 = 1.54439 Å (0.154056 nm), 154439 nm), ratio of Kα2=0.50000) was used for diffraction.
The diffractometer was set with a divergence slit of 1/2°, a divergence longitudinal limiting slit of 10 mm, a scattering slit of 2°, and a receiving slit of 0.15 mm. The goniometer radius was 169.3 mm.
Ｘ線回折測定を行う前に、還元剤のサンプル調製を行った。
まず、１００ｍｇ程度の還元剤を乳鉢に計り取り、乳棒を用いて磨り潰した。その後、還元剤を試料板の試料充填部の穴に均一に充填し、試料板の表面と還元剤による表面が同一面になるように調整した。
Ｘ線回折測定には、Ｘ線回折装置（株式会社Ｂｒｕｋｅｒ社製、「Ｄ８ ＤＩＳＣＯＶＥＲ」）を使用し、集中法により測定を実施した。対陰極には、純銅を用いた銅管球を用い、ＣｕＫαの特性Ｘ線（Ｋα１の波長（λ）＝１．５４０５６Å（０．１５４０５６ｎｍ）、Ｋα２の波長（λ）＝１．５４４３９Å（０．１５４４３９ｎｍ）、Ｋα２の比率＝０．５００００）を回折に使用した。
回折計は、発散スリットを１／２°、発散縦制限スリットを１０ｍｍ、散乱スリットを２°、受光スリット０．１５ｍｍに設定した。ゴニオメーター半径は１６９．３ｍｍであった。 4. X-Ray Diffraction Measurement Before X-ray diffraction measurement, a reducing agent sample was prepared.
First, about 100 mg of reducing agent was weighed into a mortar and ground with a pestle. After that, the reducing agent was uniformly filled into the holes of the sample filling portion of the sample plate, and the surface of the sample plate and the surface of the reducing agent were adjusted to be flush with each other.
For the X-ray diffraction measurement, an X-ray diffractometer ("D8 DISCOVER" manufactured by Bruker Co., Ltd.) was used, and the measurement was performed by the concentration method. A copper tube using pure copper was used as the anticathode, and characteristic X-rays of CuKα (wavelength (λ) of Kα1 = 1.54056 Å (0.154056 nm), wavelength (λ) of Kα2 = 1.54439 Å (0.154056 nm), 154439 nm), ratio of Kα2=0.50000) was used for diffraction.
The diffractometer was set with a divergence slit of 1/2°, a divergence longitudinal limiting slit of 10 mm, a scattering slit of 2°, and a receiving slit of 0.15 mm. The goniometer radius was 169.3 mm.
その後、管電圧４０ｋＶ、管電流を４０ｍＡの条件で、調製した還元剤のサンプルに対してＸ線を照射した。なお、ゴニオメーターの走査角度を５．５～１００．５°の範囲に設定し、走査速度３．５°／分、測定ステップ０．０１に設定して測定を行った。測定は、大気中、室温で行った。測定終了後、Ｋα１およびＫα２の分離処理を経ずに得られたデータの解析を行った。
データの解析には、ソフトウェア（Ｂｒｕｋｅｒ製、ＤＩＦＦＲＡＣ．ＥＶＡ）を用いた。
バックグラウンドを除去し、（２２０）面に対応する回折ピークの強度が最も高い値を頂点とし、このときの頂点の角度をピーク位置とした。そして、その最大ピーク値の１／２強度の２点間の間隔を半値全幅とした。この（２２０）面に対応する回折ピークにおいて、バックグラウンド除去後のピーク強度（単位：ｃｐｓ）を用いて、半値全幅に対するピーク強度の比を計算した。 After that, under the conditions of a tube voltage of 40 kV and a tube current of 40 mA, the prepared reducing agent sample was irradiated with X-rays. The scanning angle of the goniometer was set in the range of 5.5 to 100.5°, the scanning speed was set at 3.5°/min, and the measurement step was set at 0.01. Measurements were performed at room temperature in air. After the measurement was completed, data obtained without separating Kα1 and Kα2 were analyzed.
Software (DIFFRAC.EVA manufactured by Bruker) was used for data analysis.
After removing the background, the highest value of the diffraction peak intensity corresponding to the (220) plane was taken as the peak, and the angle of the peak at this time was taken as the peak position. The full width at half maximum was defined as the interval between the two points at half the intensity of the maximum peak value. In the diffraction peak corresponding to this (220) plane, the ratio of the peak intensity to the full width at half maximum was calculated using the peak intensity (unit: cps) after background removal.
データの解析には、ソフトウェア（Ｂｒｕｋｅｒ製、ＤＩＦＦＲＡＣ．ＥＶＡ）を用いた。
バックグラウンドを除去し、（２２０）面に対応する回折ピークの強度が最も高い値を頂点とし、このときの頂点の角度をピーク位置とした。そして、その最大ピーク値の１／２強度の２点間の間隔を半値全幅とした。この（２２０）面に対応する回折ピークにおいて、バックグラウンド除去後のピーク強度（単位：ｃｐｓ）を用いて、半値全幅に対するピーク強度の比を計算した。 After that, under the conditions of a tube voltage of 40 kV and a tube current of 40 mA, the prepared reducing agent sample was irradiated with X-rays. The scanning angle of the goniometer was set in the range of 5.5 to 100.5°, the scanning speed was set at 3.5°/min, and the measurement step was set at 0.01. Measurements were performed at room temperature in air. After the measurement was completed, data obtained without separating Kα1 and Kα2 were analyzed.
Software (DIFFRAC.EVA manufactured by Bruker) was used for data analysis.
After removing the background, the highest value of the diffraction peak intensity corresponding to the (220) plane was taken as the peak, and the angle of the peak at this time was taken as the peak position. The full width at half maximum was defined as the interval between the two points at half the intensity of the maximum peak value. In the diffraction peak corresponding to this (220) plane, the ratio of the peak intensity to the full width at half maximum was calculated using the peak intensity (unit: cps) after background removal.
［結晶子サイズの測定法］
ＣｕＫαの特性Ｘ線（Ｋα１の波長（λ）＝１．５４０５６Å（０．１５４０５６ｎｍ）、Ｋα２の波長（λ）＝１．５４４３９Å（０．１５４４３９ｎｍ）、Ｋα２の比率＝０．５００００）を用いて測定されたＸ線回折プロファイルにおける（２２０）面に対応する回折ピークに基づいて、下記式（１ｓ）で表されるＳｃｈｅｒｒｅｒの式により、結晶子サイズを求めた。
Ｄ＝Ｋ・λ／βｃｏｓθ ・・・（１ｓ）
β＝Ｂｏｂｓ－ｂ
［式中、Ｄは、結晶子サイズ（Å）、λは、測定Ｘ線波長（Å）、βは、結晶子サイズの大きさによる回折線幅の広がり、θは、回折角、Ｋは、Ｓｃｈｅｒｒｅｒ定数、Ｂｏｂｓは、実測の半値幅、ｂは、装置による線幅の広がりである。ここでは、Ｋは、０．８９０、ｂは、０．０５０として計算を行った。］ [Measurement method of crystallite size]
CuKα characteristic X-ray (Kα1 wavelength (λ) = 1.54056 Å (0.154056 nm), Kα2 wavelength (λ) = 1.54439 Å (0.154439 nm), Kα2 ratio = 0.50000) Based on the diffraction peak corresponding to the (220) plane in the obtained X-ray diffraction profile, the crystallite size was determined by Scherrer's formula represented by the following formula (1s).
D=K·λ/β cos θ (1 s)
β=B obs -b
[Wherein, D is the crystallite size (Å), λ is the measured X-ray wavelength (Å), β is the broadening of the diffraction line width due to the crystallite size, θ is the diffraction angle, K is the Scherrer's constant, B obs is the measured half-width, and b is the instrumental linewidth broadening. Here, K was calculated as 0.890 and b as 0.050. ]
ＣｕＫαの特性Ｘ線（Ｋα１の波長（λ）＝１．５４０５６Å（０．１５４０５６ｎｍ）、Ｋα２の波長（λ）＝１．５４４３９Å（０．１５４４３９ｎｍ）、Ｋα２の比率＝０．５００００）を用いて測定されたＸ線回折プロファイルにおける（２２０）面に対応する回折ピークに基づいて、下記式（１ｓ）で表されるＳｃｈｅｒｒｅｒの式により、結晶子サイズを求めた。
Ｄ＝Ｋ・λ／βｃｏｓθ ・・・（１ｓ）
β＝Ｂｏｂｓ－ｂ
［式中、Ｄは、結晶子サイズ（Å）、λは、測定Ｘ線波長（Å）、βは、結晶子サイズの大きさによる回折線幅の広がり、θは、回折角、Ｋは、Ｓｃｈｅｒｒｅｒ定数、Ｂｏｂｓは、実測の半値幅、ｂは、装置による線幅の広がりである。ここでは、Ｋは、０．８９０、ｂは、０．０５０として計算を行った。］ [Measurement method of crystallite size]
CuKα characteristic X-ray (Kα1 wavelength (λ) = 1.54056 Å (0.154056 nm), Kα2 wavelength (λ) = 1.54439 Å (0.154439 nm), Kα2 ratio = 0.50000) Based on the diffraction peak corresponding to the (220) plane in the obtained X-ray diffraction profile, the crystallite size was determined by Scherrer's formula represented by the following formula (1s).
D=K·λ/β cos θ (1 s)
β=B obs -b
[Wherein, D is the crystallite size (Å), λ is the measured X-ray wavelength (Å), β is the broadening of the diffraction line width due to the crystallite size, θ is the diffraction angle, K is the Scherrer's constant, B obs is the measured half-width, and b is the instrumental linewidth broadening. Here, K was calculated as 0.890 and b as 0.050. ]
５．一酸化炭素の生成量（ＣＯ生成量）
固定床流通式反応装置と、反応装置に直結するガスクロマトグラフ質量分析計（ＧＣ／ＭＳ）とを備える迅速触媒評価システムを用いて、以下の手順により還元剤による一酸化炭素の生成量を測定した。
具体的には、内径４ｍｍの石英反応管を用意し、長径３ｍｍに成型した円柱状の還元剤を積層高さが３０ｍｍになるように充填した。 5. Amount of carbon monoxide produced (amount of CO produced)
Using a rapid catalyst evaluation system equipped with a fixed-bed flow reactor and a gas chromatograph-mass spectrometer (GC/MS) directly connected to the reactor, the amount of carbon monoxide produced by the reducing agent was measured according to the following procedure. .
Specifically, a quartz reaction tube having an inner diameter of 4 mm was prepared and filled with a cylindrical reducing agent formed to have a long diameter of 3 mm so that the layer height was 30 mm.
固定床流通式反応装置と、反応装置に直結するガスクロマトグラフ質量分析計（ＧＣ／ＭＳ）とを備える迅速触媒評価システムを用いて、以下の手順により還元剤による一酸化炭素の生成量を測定した。
具体的には、内径４ｍｍの石英反応管を用意し、長径３ｍｍに成型した円柱状の還元剤を積層高さが３０ｍｍになるように充填した。 5. Amount of carbon monoxide produced (amount of CO produced)
Using a rapid catalyst evaluation system equipped with a fixed-bed flow reactor and a gas chromatograph-mass spectrometer (GC/MS) directly connected to the reactor, the amount of carbon monoxide produced by the reducing agent was measured according to the following procedure. .
Specifically, a quartz reaction tube having an inner diameter of 4 mm was prepared and filled with a cylindrical reducing agent formed to have a long diameter of 3 mm so that the layer height was 30 mm.
その後、５ｍＬ／分の流量でヘリウムガスを流しつつ、１５℃／分の昇温速度で８５０℃に昇温させ、温度安定化のため同じ温度で５分間加熱した。次に、酸素キャリアを賦活化するために、水素ガス（還元ガス）を流量５ｍＬ／分で２０分間流して酸素キャリアの還元反応（第１プロセス）を実施して、酸素キャリアを還元した。このとき、排出口から排出されるガスには、水蒸気が含まれていた。
その後、ガス交換のために、ヘリウムガスを流量５ｍＬ／分で１０分間流した後、二酸化炭素ガスを流量５ｍＬ／分で２０分間流して、二酸化炭素の還元反応（第２プロセス）を実施して、二酸化炭素ガス（原料ガス）を還元した。このとき、排出口から排出される生成ガスには、一酸化炭素が含まれていた。 Thereafter, while flowing helium gas at a flow rate of 5 mL/min, the temperature was raised to 850° C. at a rate of 15° C./min, and heated at the same temperature for 5 minutes for temperature stabilization. Next, in order to activate the oxygen carrier, hydrogen gas (reducing gas) was flowed at a flow rate of 5 mL/min for 20 minutes to carry out a reduction reaction (first process) of the oxygen carrier, thereby reducing the oxygen carrier. At this time, the gas discharged from the discharge port contained water vapor.
Thereafter, for gas exchange, helium gas is flowed at a flow rate of 5 mL/min for 10 minutes, and then carbon dioxide gas is flowed at a flow rate of 5 mL/min for 20 minutes to perform a carbon dioxide reduction reaction (second process). , the carbon dioxide gas (source gas) was reduced. At this time, carbon monoxide was contained in the generated gas discharged from the discharge port.
その後、ガス交換のために、ヘリウムガスを流量５ｍＬ／分で１０分間流した後、二酸化炭素ガスを流量５ｍＬ／分で２０分間流して、二酸化炭素の還元反応（第２プロセス）を実施して、二酸化炭素ガス（原料ガス）を還元した。このとき、排出口から排出される生成ガスには、一酸化炭素が含まれていた。 Thereafter, while flowing helium gas at a flow rate of 5 mL/min, the temperature was raised to 850° C. at a rate of 15° C./min, and heated at the same temperature for 5 minutes for temperature stabilization. Next, in order to activate the oxygen carrier, hydrogen gas (reducing gas) was flowed at a flow rate of 5 mL/min for 20 minutes to carry out a reduction reaction (first process) of the oxygen carrier, thereby reducing the oxygen carrier. At this time, the gas discharged from the discharge port contained water vapor.
Thereafter, for gas exchange, helium gas is flowed at a flow rate of 5 mL/min for 10 minutes, and then carbon dioxide gas is flowed at a flow rate of 5 mL/min for 20 minutes to perform a carbon dioxide reduction reaction (second process). , the carbon dioxide gas (source gas) was reduced. At this time, carbon monoxide was contained in the generated gas discharged from the discharge port.
次に、本試験のため、以下のプロセスを行った。
まず、ガス交換のために、ヘリウムガスを流量５ｍＬ／分で１０分間流した。
次に、水素ガス（還元ガス）を流量３ｍＬ／分で１６分間流して還元剤の還元反応（第１プロセス）を実施して、還元剤を還元した。このとき、排出口から排出されるガスには、水蒸気が含まれていた。
その後、ガス交換のために、ヘリウムガスを流量３ｍＬ／分で５分間流した後、二酸化炭素ガスを流量３ｍＬ／分で１６分間流して、二酸化炭素の還元反応（第２プロセス）を実施して、二酸化炭素ガス（原料ガス）を還元した。このとき、排出口から排出される生成ガスには、一酸化炭素が含まれていた。
なお、以上のプロセスでは、いずれのガスを流す際にも、還元剤の温度を８５０℃に維持するとともに、大気圧条件で行った。 Next, the following process was performed for this test.
First, for gas exchange, helium gas was flowed at a flow rate of 5 mL/min for 10 minutes.
Next, hydrogen gas (reducing gas) was flowed at a flow rate of 3 mL/min for 16 minutes to carry out a reducing reaction (first process) of the reducing agent, thereby reducing the reducing agent. At this time, the gas discharged from the discharge port contained water vapor.
Thereafter, for gas exchange, helium gas is flowed at a flow rate of 3 mL/min for 5 minutes, and then carbon dioxide gas is flowed at a flow rate of 3 mL/min for 16 minutes to perform a carbon dioxide reduction reaction (second process). , the carbon dioxide gas (source gas) was reduced. At this time, carbon monoxide was contained in the generated gas discharged from the discharge port.
In the above process, the temperature of the reducing agent was maintained at 850° C. and the atmospheric pressure was used when any gas was flowed.
まず、ガス交換のために、ヘリウムガスを流量５ｍＬ／分で１０分間流した。
次に、水素ガス（還元ガス）を流量３ｍＬ／分で１６分間流して還元剤の還元反応（第１プロセス）を実施して、還元剤を還元した。このとき、排出口から排出されるガスには、水蒸気が含まれていた。
その後、ガス交換のために、ヘリウムガスを流量３ｍＬ／分で５分間流した後、二酸化炭素ガスを流量３ｍＬ／分で１６分間流して、二酸化炭素の還元反応（第２プロセス）を実施して、二酸化炭素ガス（原料ガス）を還元した。このとき、排出口から排出される生成ガスには、一酸化炭素が含まれていた。
なお、以上のプロセスでは、いずれのガスを流す際にも、還元剤の温度を８５０℃に維持するとともに、大気圧条件で行った。 Next, the following process was performed for this test.
First, for gas exchange, helium gas was flowed at a flow rate of 5 mL/min for 10 minutes.
Next, hydrogen gas (reducing gas) was flowed at a flow rate of 3 mL/min for 16 minutes to carry out a reducing reaction (first process) of the reducing agent, thereby reducing the reducing agent. At this time, the gas discharged from the discharge port contained water vapor.
Thereafter, for gas exchange, helium gas is flowed at a flow rate of 3 mL/min for 5 minutes, and then carbon dioxide gas is flowed at a flow rate of 3 mL/min for 16 minutes to perform a carbon dioxide reduction reaction (second process). , the carbon dioxide gas (source gas) was reduced. At this time, carbon monoxide was contained in the generated gas discharged from the discharge port.
In the above process, the temperature of the reducing agent was maintained at 850° C. and the atmospheric pressure was used when any gas was flowed.
一酸化炭素の生成量は、二酸化炭素ガス（原料ガス）を流通させた後、単位秒あたりの一酸化炭素の生成量が０．００１ｍｍｏｌ以上となってから、０．００１ｍｍｏｌ以下になるまでに、生成した一酸化炭素の合計量を還元剤の重量（ｇ）で除算した値で規定した。
After the carbon monoxide gas (raw material gas) is circulated, the amount of carbon monoxide produced is from 0.001 mmol or more per second to 0.001 mmol or less. It was defined as a value obtained by dividing the total amount of carbon monoxide produced by the weight (g) of the reducing agent.
なお、ガスクロマトグラフ質量分析（ＧＣ／ＭＳ分析）は、島津製作所製、「ＱＰ－２０２０」を使用した。ＧＣ部における条件は、以下の通りである。
カラム温度： ２００℃
インジェクション温度： ２００℃
検出器温度： ２５０℃
カラム： ＥＧＡチューブ（Ｌ：２．５ｍ、φ（内径）：０．１５ｍｍ、ｔ：０ｍｍ）
カラム流量： ０．５５ｍＬ／分
スプリット比： ４００
パージ流量： ５．０ｍＬ／分 For gas chromatograph mass spectrometry (GC/MS analysis), "QP-2020" manufactured by Shimadzu Corporation was used. Conditions in the GC section are as follows.
Column temperature: 200°C
Injection temperature: 200°C
Detector temperature: 250°C
Column: EGA tube (L: 2.5 m, φ (inner diameter): 0.15 mm, t: 0 mm)
Column flow rate: 0.55 mL/min Split ratio: 400
Purge flow rate: 5.0 mL/min
カラム温度： ２００℃
インジェクション温度： ２００℃
検出器温度： ２５０℃
カラム： ＥＧＡチューブ（Ｌ：２．５ｍ、φ（内径）：０．１５ｍｍ、ｔ：０ｍｍ）
カラム流量： ０．５５ｍＬ／分
スプリット比： ４００
パージ流量： ５．０ｍＬ／分 For gas chromatograph mass spectrometry (GC/MS analysis), "QP-2020" manufactured by Shimadzu Corporation was used. Conditions in the GC section are as follows.
Column temperature: 200°C
Injection temperature: 200°C
Detector temperature: 250°C
Column: EGA tube (L: 2.5 m, φ (inner diameter): 0.15 mm, t: 0 mm)
Column flow rate: 0.55 mL/min Split ratio: 400
Purge flow rate: 5.0 mL/min
また、МＳ部（検出部）については、以下の条件で検量した状態で使用した。
すなわち、二酸化炭素で校正された、吐出フルスケールが１０ｍＬ／ｍｉｎまたは５０ｍＬ／ｍｉｎ、流量精度が±１．０％、再現精度が±０．２％のマスフローコントローラーを用いて、二酸化炭素を１、２、３ｍＬ／ｍｉｎで流した際の検出信号強度をプロットし、最小二乗法を用いて原点を通る直線で近似した際の検量線が、Ｒ２>０．９８なる関係を満足するよう、検出信号強度を調節した。これに基づき、二酸化炭素の検出信号強度に対する、検出量（単位秒あたりの二酸化炭素の生成量）を算出した。
また、一酸化炭素についても同様に以下の手順で検量した。当該マスフローコントローラーを用いて一酸化炭素を１、２、３、５ｍＬ／ｍｉｎで流した際の検出信号強度をプロットし、最小二乗法を用いて原点を通る直線で近似した際の検量線が、Ｒ２>０．９８なる関係を満足していること、の両方を満たすよう、検出信号強度を調節した。これに基づき、一酸化炭素の検出信号強度に対する、検出量（単位秒あたりの一酸化炭素の生成量）を算出した。
ただし、上記二酸化炭素や一酸化炭素等のガスは、マスフローコントローラーから、上記条件に設定したＧＣ部を経由してМＳ部に投入されるものとし、また、一酸化炭素を流す際にはコンバージョン・ファクターを用いてマスフローコントローラーの設定を変更するものとし、二酸化炭素、一酸化炭素それぞれのコンバージョン・ファクターの値は０．７４および１．００とする。 In addition, the МS part (detection part) was used after being calibrated under the following conditions.
That is, using a mass flow controller calibrated with carbon dioxide, with a discharge full scale of 10 mL / min or 50 mL / min, a flow rate accuracy of ± 1.0%, and a repeatability of ± 0.2%, carbon dioxide is Plot the detected signal intensity when flowing at 2, 3 mL / min, and use the least squares method to approximate the calibration curve with a straight line passing through the origin . Signal strength was adjusted. Based on this, the detected amount (the amount of carbon dioxide produced per second) was calculated with respect to the detected signal intensity of carbon dioxide.
Also, carbon monoxide was similarly calibrated by the following procedure. Plot the detected signal intensity when carbon monoxide is flowed at 1, 2, 3, 5 mL / min using the mass flow controller, and approximate it with a straight line passing through the origin using the least squares method. The detected signal intensity was adjusted so as to satisfy both the relationship R 2 >0.98. Based on this, the detected amount (the amount of carbon monoxide produced per second) was calculated with respect to the detected signal intensity of carbon monoxide.
However, the above gases such as carbon dioxide and carbon monoxide shall be supplied from the mass flow controller to the МS section via the GC section set to the above conditions. A factor is used to change the setting of the mass flow controller, with conversion factor values of 0.74 and 1.00 for carbon dioxide and carbon monoxide, respectively.
すなわち、二酸化炭素で校正された、吐出フルスケールが１０ｍＬ／ｍｉｎまたは５０ｍＬ／ｍｉｎ、流量精度が±１．０％、再現精度が±０．２％のマスフローコントローラーを用いて、二酸化炭素を１、２、３ｍＬ／ｍｉｎで流した際の検出信号強度をプロットし、最小二乗法を用いて原点を通る直線で近似した際の検量線が、Ｒ２>０．９８なる関係を満足するよう、検出信号強度を調節した。これに基づき、二酸化炭素の検出信号強度に対する、検出量（単位秒あたりの二酸化炭素の生成量）を算出した。
また、一酸化炭素についても同様に以下の手順で検量した。当該マスフローコントローラーを用いて一酸化炭素を１、２、３、５ｍＬ／ｍｉｎで流した際の検出信号強度をプロットし、最小二乗法を用いて原点を通る直線で近似した際の検量線が、Ｒ２>０．９８なる関係を満足していること、の両方を満たすよう、検出信号強度を調節した。これに基づき、一酸化炭素の検出信号強度に対する、検出量（単位秒あたりの一酸化炭素の生成量）を算出した。
ただし、上記二酸化炭素や一酸化炭素等のガスは、マスフローコントローラーから、上記条件に設定したＧＣ部を経由してМＳ部に投入されるものとし、また、一酸化炭素を流す際にはコンバージョン・ファクターを用いてマスフローコントローラーの設定を変更するものとし、二酸化炭素、一酸化炭素それぞれのコンバージョン・ファクターの値は０．７４および１．００とする。 In addition, the МS part (detection part) was used after being calibrated under the following conditions.
That is, using a mass flow controller calibrated with carbon dioxide, with a discharge full scale of 10 mL / min or 50 mL / min, a flow rate accuracy of ± 1.0%, and a repeatability of ± 0.2%, carbon dioxide is Plot the detected signal intensity when flowing at 2, 3 mL / min, and use the least squares method to approximate the calibration curve with a straight line passing through the origin . Signal strength was adjusted. Based on this, the detected amount (the amount of carbon dioxide produced per second) was calculated with respect to the detected signal intensity of carbon dioxide.
Also, carbon monoxide was similarly calibrated by the following procedure. Plot the detected signal intensity when carbon monoxide is flowed at 1, 2, 3, 5 mL / min using the mass flow controller, and approximate it with a straight line passing through the origin using the least squares method. The detected signal intensity was adjusted so as to satisfy both the relationship R 2 >0.98. Based on this, the detected amount (the amount of carbon monoxide produced per second) was calculated with respect to the detected signal intensity of carbon monoxide.
However, the above gases such as carbon dioxide and carbon monoxide shall be supplied from the mass flow controller to the МS section via the GC section set to the above conditions. A factor is used to change the setting of the mass flow controller, with conversion factor values of 0.74 and 1.00 for carbon dioxide and carbon monoxide, respectively.
（２２０）面に対応する回折ピークのピーク位置、その半値全幅、結晶子ザイズ、ピーク強度／半値全幅、および一酸化炭素の生成量を、以下の表１に示す。
各実施例の還元剤は、比較例１の酸化セリウム単体の還元剤に比べて、一酸化炭素の生成量が多かった。
The peak position of the diffraction peak corresponding to the (220) plane, its full width at half maximum, crystallite size, peak intensity/full width at half maximum, and the amount of carbon monoxide produced are shown in Table 1 below.
The reducing agent of each example produced a larger amount of carbon monoxide than the reducing agent of Comparative Example 1, which was cerium oxide alone.
５．酸素欠損量
実施例１および比較例１で得られた還元剤の酸素欠損量は、熱重量測定（ＴＧ）を用いて測定した。還元剤の水素によって還元されて質量が減少したときの質量と、二酸化炭素によって再酸化されて質量が増加したときの質量との差を、充填した還元剤に含まれる酸素キャリアの質量で除算し、１００倍することにより酸素欠損量（％）を求めた。
具体的には、まず、試料容器に１００ｍｇの還元剤を充填した。次に、ヘリウムを流しながら１０℃／分で８５０℃または６５０℃まで昇温させた。 5. Amount of Oxygen Deficit The amount of oxygen vacancy of the reducing agents obtained in Example 1 and Comparative Example 1 was measured using thermogravimetry (TG). The difference between the mass reduced by the reducing agent hydrogen and the mass increased by carbon dioxide is divided by the mass of the oxygen carrier contained in the charged reducing agent. , 100 to obtain the amount of oxygen deficiency (%).
Specifically, first, a sample container was filled with 100 mg of a reducing agent. Next, the temperature was raised to 850° C. or 650° C. at 10° C./min while flowing helium.
実施例１および比較例１で得られた還元剤の酸素欠損量は、熱重量測定（ＴＧ）を用いて測定した。還元剤の水素によって還元されて質量が減少したときの質量と、二酸化炭素によって再酸化されて質量が増加したときの質量との差を、充填した還元剤に含まれる酸素キャリアの質量で除算し、１００倍することにより酸素欠損量（％）を求めた。
具体的には、まず、試料容器に１００ｍｇの還元剤を充填した。次に、ヘリウムを流しながら１０℃／分で８５０℃または６５０℃まで昇温させた。 5. Amount of Oxygen Deficit The amount of oxygen vacancy of the reducing agents obtained in Example 1 and Comparative Example 1 was measured using thermogravimetry (TG). The difference between the mass reduced by the reducing agent hydrogen and the mass increased by carbon dioxide is divided by the mass of the oxygen carrier contained in the charged reducing agent. , 100 to obtain the amount of oxygen deficiency (%).
Specifically, first, a sample container was filled with 100 mg of a reducing agent. Next, the temperature was raised to 850° C. or 650° C. at 10° C./min while flowing helium.
その後、８５０℃または６５０℃を維持したまま、水素とヘリウムとの混合ガス（水素１０容積％）を１００ｍＬ／分で１０分間流し、還元剤を還元した。１０分後、ガス交換のためにヘリウムガスを１００ｍＬ／分で３０分間流した。このときの還元剤の重量を「Ａ」とする。
次に、二酸化炭素とヘリウムとの混合ガス（二酸化炭素１０体積％）を１００ｍＬ／分で１０分間流し、還元剤を酸化した。１０分後、ガス交換のためにヘリウムガスを１００ｍＬ／分で３０分間流した。このときの還元剤の重量を「Ｂ」とする。
そして、酸素欠損量（％）は、（Ｂ－Ａ／還元剤に含まれる酸素キャリアの質量）×１００で求めた。 Thereafter, while maintaining the temperature at 850° C. or 650° C., a mixed gas of hydrogen and helium (10% by volume of hydrogen) was flowed at 100 mL/min for 10 minutes to reduce the reducing agent. After 10 minutes, helium gas was flowed at 100 mL/min for 30 minutes for gas exchange. The weight of the reducing agent at this time is defined as "A".
Next, a mixed gas of carbon dioxide and helium (10% by volume of carbon dioxide) was flowed at 100 mL/min for 10 minutes to oxidize the reducing agent. After 10 minutes, helium gas was flowed at 100 mL/min for 30 minutes for gas exchange. The weight of the reducing agent at this time is defined as "B".
The amount of oxygen deficiency (%) was determined by (BA/mass of oxygen carrier contained in reducing agent)×100.
次に、二酸化炭素とヘリウムとの混合ガス（二酸化炭素１０体積％）を１００ｍＬ／分で１０分間流し、還元剤を酸化した。１０分後、ガス交換のためにヘリウムガスを１００ｍＬ／分で３０分間流した。このときの還元剤の重量を「Ｂ」とする。
そして、酸素欠損量（％）は、（Ｂ－Ａ／還元剤に含まれる酸素キャリアの質量）×１００で求めた。 Thereafter, while maintaining the temperature at 850° C. or 650° C., a mixed gas of hydrogen and helium (10% by volume of hydrogen) was flowed at 100 mL/min for 10 minutes to reduce the reducing agent. After 10 minutes, helium gas was flowed at 100 mL/min for 30 minutes for gas exchange. The weight of the reducing agent at this time is defined as "A".
Next, a mixed gas of carbon dioxide and helium (10% by volume of carbon dioxide) was flowed at 100 mL/min for 10 minutes to oxidize the reducing agent. After 10 minutes, helium gas was flowed at 100 mL/min for 30 minutes for gas exchange. The weight of the reducing agent at this time is defined as "B".
The amount of oxygen deficiency (%) was determined by (BA/mass of oxygen carrier contained in reducing agent)×100.
酸素欠損量を、以下の表２に示す。
The amount of oxygen deficiency is shown in Table 2 below.
各実施例の還元剤に含まれる酸素キャリアは、比較例１の還元剤を構成する酸化セリウム単体に比べて、酸素欠損量が多かった。この結果は、二酸化炭素の一酸化炭素への変換効率が高い結果とよく一致する。
The oxygen carrier contained in the reducing agent of each example had a larger amount of oxygen deficiency than the cerium oxide alone constituting the reducing agent of Comparative Example 1. This result is in good agreement with the high conversion efficiency of carbon dioxide to carbon monoxide.
Claims (14)
- 接触により二酸化炭素を還元して炭素有価物を生成する還元剤であって、
セリウム（Ｃｅ）およびセリウム（Ｃｅ）以外の遷移元素を含む金属酸化物で構成され、酸素イオン伝導性を備える酸素キャリアを含有し、
前記酸素キャリアのＸ線回折測定を行ったとき、Ｘ線回折プロファイルにおいて、（２２０）面に対応する少なくとも１つの回折ピークのピーク位置が、酸化セリウム（ＣｅＯ２）の（２２０）面に対応する回折ピークのピーク位置に対してシフトしている、還元剤。 A reducing agent that reduces carbon dioxide on contact to produce carbon valuables,
composed of cerium (Ce) and a metal oxide containing a transition element other than cerium (Ce) and containing an oxygen carrier having oxygen ion conductivity;
When the X-ray diffraction measurement of the oxygen carrier is performed, the peak position of at least one diffraction peak corresponding to the (220) plane in the X-ray diffraction profile corresponds to the (220) plane of cerium oxide (CeO 2 ). A reducing agent that is shifted with respect to the peak position of the diffraction peak. - 請求項１に記載の還元剤において、
前記酸化セリウム（ＣｅＯ２）の（２２０）面に対応する回折ピークのピーク位置に対する、前記酸素キャリアの前記（２２０）面に対応する回折ピークのピーク位置のシフト量は、２θで０．１°以上０．６°未満である、還元剤。 The reducing agent according to claim 1,
The shift amount of the peak position of the diffraction peak corresponding to the (220) plane of the oxygen carrier with respect to the peak position of the diffraction peak corresponding to the (220) plane of the cerium oxide (CeO 2 ) is 0.1° in 2θ. A reducing agent that is greater than or equal to less than 0.6°. - 請求項１または請求項２に記載の還元剤において、
前記酸素キャリアの前記（２２０）面に対応する回折ピークは、その半値全幅が０．３以上である、還元剤。 In the reducing agent according to claim 1 or claim 2,
The reducing agent, wherein the diffraction peak corresponding to the (220) plane of the oxygen carrier has a full width at half maximum of 0.3 or more. - 請求項１～請求項３のいずれか１項に記載の還元剤において、
前記酸素キャリアは、その結晶子サイズが３２０Å以下である、還元剤。 In the reducing agent according to any one of claims 1 to 3,
The reducing agent, wherein the oxygen carrier has a crystallite size of 320 Å or less. - 請求項１～請求項４のいずれか１項に記載の還元剤において、
前記酸素キャリアの前記（２２０）面に対応する回折ピークにおいて、その半値全幅に対するピーク強度の比が６．２以下である、還元剤。 In the reducing agent according to any one of claims 1 to 4,
A reducing agent, wherein the diffraction peak corresponding to the (220) plane of the oxygen carrier has a ratio of peak intensity to full width at half maximum of 6.2 or less. - 請求項１～請求項５のいずれか１項に記載の還元剤において、
前記遷移元素は、周期表の第４周期および第５周期に属する元素のうちの少なくとも１種である、還元剤。 In the reducing agent according to any one of claims 1 to 5,
The reducing agent, wherein the transition element is at least one element belonging to the 4th period and the 5th period of the periodic table. - 請求項１～請求項６のいずれか１項に記載の還元剤において、
前記炭素有価物は、一酸化炭素を含む、還元剤。 In the reducing agent according to any one of claims 1 to 6,
The reducing agent, wherein the carbon value includes carbon monoxide. - 請求項１～請求項７のいずれか１項に記載の還元剤において、
前記二酸化炭素との接触は、６５０℃を上回る温度で行われる、還元剤。 In the reducing agent according to any one of claims 1 to 7,
A reducing agent, wherein said contact with carbon dioxide is carried out at a temperature above 650°C. - 請求項１～請求項８のいずれか１項に記載の還元剤において、
前記二酸化炭素との接触により酸化された前記還元剤は、水素を含む還元ガスと接触させることにより還元される、還元剤。 In the reducing agent according to any one of claims 1 to 8,
The reducing agent, wherein the reducing agent oxidized by contact with carbon dioxide is reduced by contacting with a reducing gas containing hydrogen. - 請求項９に記載の還元剤において、
前記水素を含む還元ガスとの接触は、６５０℃を上回る温度で行われる、還元剤。 In the reducing agent according to claim 9,
A reducing agent, wherein the contact with the reducing gas comprising hydrogen is at a temperature above 650°C. - 請求項９または請求項１０に記載の還元剤において
前記水素を含む還元ガスと接触させることにより、前記還元剤に含まれる前記酸素キャリアの質量に対して０．４５％以上の可逆的な酸素欠損量を生じる、還元剤。 11. In the reducing agent according to claim 9 or 10, by contacting with the reducing gas containing hydrogen, reversible oxygen deficiency of 0.45% or more with respect to the mass of the oxygen carrier contained in the reducing agent A reducing agent that yields a quantity. - 請求項１～請求項１１のいずれか１項に記載の還元剤において、
さらに、前記酸素キャリアを結合する結合剤を含有する、還元剤。 In the reducing agent according to any one of claims 1 to 11,
A reducing agent further comprising a binder that binds the oxygen carrier. - 請求項１２に記載の還元剤において、
前記還元剤に含まれる前記結合剤の割合は、前記還元剤１００質量部に対して１質量部以上６０質量部以下である、還元剤。 The reducing agent according to claim 12,
The reducing agent, wherein the ratio of the binder contained in the reducing agent is 1 part by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the reducing agent. - 二酸化炭素を含む原料ガスを還元剤と接触させることにより、前記二酸化炭素を還元して炭素有価物を含む生成ガスを製造するガスの製造方法であって、
前記還元剤は、セリウム（Ｃｅ）およびセリウム（Ｃｅ）以外の遷移元素を含む金属酸化物で構成され、酸素イオン伝導性を備える酸素キャリアを含有し、
前記酸素キャリアのＸ線回折測定を行ったとき、Ｘ線回折プロファイルにおいて、（２２０）面に対応する少なくとも１つの回折ピークのピーク位置が、酸化セリウム（ＣｅＯ２）の（２２０）面に対応する回折ピークのピーク位置に対してシフトしている、ガスの製造方法。 A gas production method for producing a product gas containing carbon valuables by reducing carbon dioxide by bringing a raw material gas containing carbon dioxide into contact with a reducing agent,
The reducing agent is composed of cerium (Ce) and a metal oxide containing a transition element other than cerium (Ce) and contains an oxygen carrier having oxygen ion conductivity,
When the X-ray diffraction measurement of the oxygen carrier is performed, the peak position of at least one diffraction peak corresponding to the (220) plane in the X-ray diffraction profile corresponds to the (220) plane of cerium oxide (CeO 2 ). A method for producing a gas in which the diffraction peaks are shifted with respect to the peak position.
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